10.6092/issn.1973-9494/10672
This paper presents the method adopted in the study of Ibo, a small island of the Quirimbas Archipelago in northern Mozambique. Ibo is part of a larger study, begun in 2004 which is still ongoing. In the first phase, the author's attention was focused on the restoration of the historic architecture built with coral limestone. But very soon it became evident that it was necessary to study the context in which these coral architectures were built. After a few years of careful observation, it was apparent that coral stone architecture is strongly conditioned by the knowledge and conservation of the natural environment in which it is built. And in the case of Ibo, the beauty of its heritage and its conservation lies in the delicate balance between architecture and nature.
application/pdf
1973-9494
10672
en
Maurizio Berti
Conservation Science in Cultural Heritage
coral stone
Ibo Island in the Quirimbas Archipelago. An Architectural Heritage Within a Natural Heritage
Text.Serial.Journal
https://conservation-science.unibo.it/
19
Articles
2020-03-18
2020-03-17
2020-03-18
2020-03-18
251-266
CSCH
Maurizio Berti
2019
10.6092/issn.1973-9494/10672
251
Independent researcher, Padua
1973-9494
coral stone
en
266
Ibo Island in the Quirimbas Archipelago. An Architectural Heritage Within a Natural Heritage
https://conservation-science.unibo.it/article/download/10672/10610
19
I    O ISLAND IN THE QUIRIMBAS ARCHIPELAGO:
    B
    AN ARCHITECTURAL HERITAGE WITHIN A NATURAL
    HERITAGE

    Maurizio Berti*1
    Independent researcher, Padua, Italy




    Keywords: Ibo, Quirimbas, architectural heritage, natural heritage, coral stone


    1. Introduction

    Interest in the architectural heritage built with coral stone in Mozambique began in
2004 on seeing the disintegration of the walls of houses and public buildings in the city
of Inhambane [1]. From first observations, it was clear that the main cause of this disin-
tegration was due to the presence of water-soluble salts. In aqueous solution, salts can
be absorbed from the environment, but they may be present in the building materials
before being used for construction, in solution or a crystalline state. The observations
were extended from Inhambane to Ibo and the Island of Mozambique, where the same
phenomenon was found.
    The geographic regions affected by similar phenomena are distributed along the
coasts included in the tropical zone and the topic deserves more attention, although it
has recently gained some space in the literature on heritage conservation [2,3].
    A wall of coral limestone can be contextualized in its physical environment through
the technological and historical tools used by conservation specialists. However, a
wider knowledge of the different ways in which nature and culture meet is an interest-
ing path to explore not only for scholars but also for tourists and especially for the
resident community.
    The same phenomena are present in Inhambane and the Island of Mozambique
and Ibo, but in Ibo, the correlation between the natural context and the local culture is
more surprising than in other places. The culture, architecture and nature of Ibo are
resources combined in a simple but peculiar equilibrium. The protection of this balance
could be considered as an initial investment to preserve the value of the entire natural
and cultural heritage. Understanding the interactions between nature and architecture
can therefore begin with simple observations [4].


*    Corresponding author: maurizio.berti100@gmail.com
                                                                                                             2. The condition of the island


                                                                                                             2.1. An island between the reef crest and the back reef

                                                                                                               Ibo is part of the Quirimbas Archipelago, in the tropical area of northern Mo-
                                                                                                           zambique. Its surface is about 15 square km and it is one of the largest islands
                                                                                                           in the archipelago. The shortest distance between the island and the mainland is
M. Berti - Ibo island in the Quirimbas archipelago: an architectural heritage within a natural heritage




                                                                                                           about 400 m. The island is surrounded by coral reefs in the northeast and large
                                                                                                           mangrove forests in the southwest. Some geographic features of the island and its
                                                                                                           district make transport routes and communication difficult.
                                                                                                               On Ibo, like on the other islands of the Quirimbas Archipelago, there are no per-
                                                                                                           manent streams of fresh water. However, on some islands, including Ibo, ground-
                                                                                                           water can be drawn from wells but it is not always drinkable. In Ibo, there are
                                                                                                           infiltration lines, especially in the mangrove plains to the north and east, where
                                                                                                           tidal flow and rainwater meet. In the southeast, partially separated from the sea by
                                                                                                           dunes, there is an open grassy plain. In the northwest, there is an agricultural area
                                                                                                           and a dense area of vegetation bordering the runway for small aeroplanes. The
                                                                                                           eastern part of the island is surrounded by a coral sedimentation platform over-
                                                                                                           looking the ocean and at low tide, allows the collection of seafood and shellfish.
                                                                                                               Like other islands in the archipelago, Ibo consists of a coral limestone rock
                                                                                                           deposit. There are dune formations, in some cases covered with humus produced
                                                                                                           by tropical vegetation. Excluding the mangrove forests, a thin layer of moderately
                                                                                                           fertile soil covers the whole island.
                                                                                                               The ongoing process of diagenesis in coral fragments and deposits of differ-
                                                                                                           ent origins is at an early stage and therefore the soil is permeable and not very
                                                                                                           compact. However, some limestone rocks often have a good degree of hardness
                                                                                                           and, in some deposits, are compact with a homogeneous structure, such as in the
                                                                                                           limestone platform on the east of the island.
                                                                                                               The north and north-east coasts are bordered by coral rocks eroded by the
                                                                                                           waves and are hard with irregular edges. These rock barriers over time have
                                                                                                           caused the formation of the madreporic sedimentation towards the lagoon which
                                                                                                           protects the areas behind them from high tides and storms and given the island its
                                                                                                           appearance as we see it today. To the north, in the coastal areas between the two
                                                                                                           rocky peaks, there are flat dunes and a coralline limestone platform that is partially
                                                                                                           colonised by mangroves and a sandy beach.
                                                                                                               The so-called Porto Interior is located on the west coast, with an entrance fac-
                                                                                                           ing north. The west coast is characterised by deposits of sand and mud and, at
                                                                                                           the same time, is subject to the effects of tidal erosion. The harbour is the terminal
                                                                                                           part of one of the main tidal channels between the ocean and the lagoon, while on
                                                                                                           the opposite side there extends a large mangrove forest. Along the harbour, a wall
                                                                                                           with buttresses protects the island from tidal erosion (Figure 1).
                                                                                                               Near the church, the quay is mostly occupied by old commercial houses with
                                                                                                           their moorings. The protective wall with buttresses is now at risk of collapse. In
                                                                                                           some places, the wall has completely disappeared, but the foundation base, made
                                                                                                           of hard square stones assembled with a strong binder, is still present.
                                                                                                               The collapse of the harbour walls due to the action of the tide, necessitates
                                                                                                           immediate action. Low-intensity earthquakes have occurred in this area, but it


                                                                                                     252
appears that they have not damaged the buildings. Although the lack of specific
studies suggests that this phenomenon does not seem relevant to the island, it is
still useful to study historical earthquake data in the region.




Figure 1. Porto Interior, Ibo Island. Porto Interior, Ibo Island. The buttresses prevent the collapse
of the out-of-plane walls of the warehouses



   2.2. The urban heritage

   Ibo’s architecture and urban landscape have been carefully studied over the
past three decades and are still being researched. Fundamental studies were con-
ducted by the Portuguese sociologist Carlos Lopes Bento [5] and the Mozambican
architect Júlio Carrilho [6,7]. For those interested in the historic architecture of Ibo,
Bento offers a vast collection of documents that reconstruct the formation of this




                                                                                                              CONSERVATION SCIENCE IN CULTURAL HERITAGE
town during the era of Portuguese colonialism. After resuming Bento’s studies,
Carrilho has made an analysis of the most recent conditions on the island.
   As for architecture, Carrilho also carries out interesting research on the formal
models of colonial residences, hypothetically finding a synthesis between different
cultures:
   Portuguese, Swahili and Indian. The historic architecture of Ibo is relatively
recent and was largely built during the period in which the town played a signifi-
cant role in the slave trade in the second half of the nineteenth century (Figure 2).
But Carrilho’s attention turned to other aspects in the formation of the urban ag-
gregate: the relationship of the three forts with the main roads, the recognition of
the Swahili-type house in indigenous neighbourhoods, materials and construction
techniques, a comparison of old and current photos of the same architecture, etc.
   These studies were integrated into Ibo’s urban plan (Plano de Urbanização
da Vila do Ibo), which was commissioned by the Cabo Delgado government and
coordinated by Carrilho himself [8].
   To protect the architectural and landscape heritage of Ibo and for the rational
development of the island’s population, the plan defines the urban area based on
the different historical and functional characteristics.




                                                                                                        253
M. Berti - Ibo island in the Quirimbas archipelago: an architectural heritage within a natural heritage




                                                                                                                            Figure 2. The ancient Maria Pia residential street today.



                                                                                                              The town of Ibo is an urban complex which originated from two very different
                                                                                                           historical systems: the formal or planned system and the informal or unplanned
                                                                                                           system. The two systems are enclosed in two distinct urban areas and constitute
                                                                                                           the classic division of the colonial town: on the one side, the European and Asian
                                                                                                           population; on the other the indigenous population.
                                                                                                              Revising the colonial division of two parts, the plan provides the creation of a
                                                                                                           third urban area in which to place the most useful infrastructures to improve life
                                                                                                           both in the formal and informal area. Consequently, the town is constituted by
                                                                                                           three large areas each with their own historical characteristics, namely: (i) the
                                                                                                           Formal Area, (ii) the Informal Area, (iii) the Transitional Area (Figure 3).
                                                                                                              (i) The Formal Area, of approximately 23.3 ha, is made up of stone and lime
                                                                                                           constructions following a project and specific standards. A relatively small part of
                                                                                                           the population lives there. The Formal Area has an identifiable structure and the
                                                                                                           buildings have relatively homogeneous styles, presenting a clear overall unity.
                                                                                                           Formed by the most ancient and refined architecture, this area is largely aban-
                                                                                                           doned, even though ownership transfers and the restoration of some buildings
                                                                                                           resumed in the late 1990s.
                                                                                                              (ii) The Informal Area, of about 68.4 ha, has buildings made with stone and
                                                                                                           lime or structured with wooden poles (pau-a-pique), mostly covered with palm
                                                                                                           leaves (macúti), and is the result of a spontaneous process of occupation. More
                                                                                                           than 2500 inhabitants live in the area, the equivalent of about 75% of the island’s
                                                                                                           population. The designation for this type of urban area is questionable. The infor-
                                                                                                           mal settlement is, in most cases, the consequence of complex family processes in
                                                                                                           which the public authority is not always present. But this area shows great dyna-
                                                                                                           mism in social relations.
                                                                                                              (iii) The Transitional Area, of about 13.6 ha, now establishes the interface be-
                                                                                                           tween the Formal Area and the Informal Area, with constructions generally in
                                                                                                           stone and lime resulting from the recent expansion of the Formal Area, but without



                                                                                                     254
a clear urban structure or recognizable spatial organization. Large spaces in this
area can be planned to improve the entire urban layout [8].




Figure 3. From the urban plan of the town of Ibo (2008): a re-working of the partial graphic map
of the intended use of the soil and the settlement.



   3. The situation between human and natural environment




                                                                                                         CONSERVATION SCIENCE IN CULTURAL HERITAGE
   With the adoption of the Plano de Urbanização in 2008, an administrative pro-
cess was formally completed. Although the plan has exhaustively collected his-
torical data and recent research results, it seems useful to consider the topic of
building materials once more. The extraction of materials from the ground, and
their use, constitutes a relatively new topic in this region, but it is causing grow-
ing interest in environmentalists and scholars. In Ibo, addressing the question
of materials in empirical but factual terms has helped to fix the cultural trends in
progress and to concretely implement the adopted urban plan.
   The surveys and discussions carried out during the three trips to the island of
Ibo, two in 2007 (the second visit was made with the technical team in charge of
developing Ibo’s urban plan) and the last in 2009, indicated that the above simple
arguments can help to interpret heritage as a combination of the natural and cul-
tural systems (Figure 4).
   The island of Ibo seems the ideal place to treat each artefact or set of artefacts
in their natural context, paying attention to the present (the object), the past (his-
tory) and the future (the project). Establishing the age of the island’s heritage
means introducing into the urban and environmental plan awareness of the pre-
sent and of the past which will help to prefigure Ibo’s future in a more critical and
responsible way.




                                                                                                   255
M. Berti - Ibo island in the Quirimbas archipelago: an architectural heritage within a natural heritage




                                                                                                           Figure 4. Field observations made by the author at Ibo Island during study visits. Paths drawn on
                                                                                                           Google Earth map, 2007-2019.



                                                                                                              Cultural and natural heritage includes every past and present artefact as part of a ge-
                                                                                                           ographical context. Bearing this in mind, we can imagine a definition for the cultural and
                                                                                                           natural heritage of the island of Ibo, where the geographical context undergoes a con-
                                                                                                           tinuous natural transformation and where, today, urban culture is of a low level due to the
                                                                                                           economic situation of the people which is almost at the limit of human survival. Visiting
                                                                                                           the town of Ibo, we immediately perceive the difference between the many abandoned
                                                                                                           Portuguese buildings and the inhabited indigenous ones. It is, however, misleading to
                                                                                                           focus attention only on the styles we define with the terms Portuguese and indigenous.
                                                                                                           Carrilho’s studies and the Plano de Urbanização give useful indications in recognizing
                                                                                                           traces of the contamination between Portuguese settlers, Swahili people, Indian traders,
                                                                                                           and ethnic groups such as Makua, Mwani, Makonde. But what is the awareness of the
                                                                                                           cultural and natural heritage of those who now live on the island?


                                                                                                              3.1. Looking for a link between the human and the natural environment

                                                                                                              To try to understand how the population of the island maintains a balance between
                                                                                                           the town and the natural environment, let us first consider a list of places that feed
                                                                                                           the construction process, the maintenance of buildings and the possible develop-
                                                                                                           ment of the town (Figure 4).

                                                                                                     256
    3.1.1. Monumental Sites
    In addition to the monumental buildings listed in the Plano and already recognized
as such in the nineteenth century maps of the island, we found some artefacts of
historical and monumental interest that deserve more attention, especially from the
population: the Hindu cemetery, the Islamic cemetery, the fortified building called
Casa das Cobras, the lighthouse keeper’s house, the Catholic cemetery, scattered
tombs near the Catholic cemetery crossed by the road leading to the airport (Figure
4). These sites are abandoned like the colonial monuments listed in the Plano. A
systematic survey could accurately define the entire system of cemeteries, either in
use or abandoned, as monumental areas protected by the public administration, so
that they can be easily identified as the historical and cultural heritage of the different
religious communities living on the island.

   3.1.2. Expansion of the island
   Several areas have been identified where the mangrove forest is expanding;
new mangroves can be found growing on the mineralized coral reef platforms in
the North and East. It would be important to establish to what extent the mangroves
have expanded to the south and west, where in some places, we can see the ero-
sion caused by the sea and some accumulations of soil deposited by the flow of
rainwater. Configuration processes in the balance between various natural phe-
nomena must be determined to identify the most suitable areas to use or exploit,
for example, for cutting wood, needed in the maintenance of buildings.

   3.1.3. Lime kilns
   We have identified four open-air kilns for cooking lime. Unlike closed kilns, open
ones are not very efficient. They require large amounts of fuelwood and do not al-
low uniform combustion of the processed mineral. We also noted that a substantial
part of the coral material had not been burned completely and would therefore




                                                                                                    CONSERVATION SCIENCE IN CULTURAL HERITAGE
probably not be used but discarded. This is due to the fact that if the non-calcined
limestone is mixed with the calcined limestone, the lime is likely to have poor me-
chanical properties. There is, however, an advantage in open kilns because the
calcined limestone is able to make good use of rainwater in the final hydration
process, but the casual aspects of this final step make the benefit uncertain. We
consequently believe that a closed kiln is preferable. The creation of a closed kiln
for cooking lime gives some interesting advantages: lime production is simpler and
more controlled, the lime has a constant level of quality and, finally, a large quantity
of firewood is saved.

   3.1.4. The coral reef and the limestone quarries
   We noted that the limestone loads in the three open kilns consisted of fragments
and debris of mineralized corals. According to the information of local producers,
the limestone for these kilns is usually collected in the most accessible part of the
coral reef along the north and east sides of the island, preferably coral skeletons
with thin pores. In order to restore public or private historic buildings, it is essential
to define precisely the conditions and methods for collecting limestone as well as
minimize the degradation of the coral reefs and madreporic deposits in case of a
possible increase in demand.



                                                                                              257
                                                                                                              3.1.5. The sand quarries
                                                                                                              For security reasons, after the ban on extracting sand from the pit near the houses
                                                                                                           in the Formal Area of the town (Figure 4, Sandpit 2), the Administration authorized
                                                                                                           excavations in an area behind the Catholic cemetery at the edge of the sea (Figure
                                                                                                           4, Sandpit 1). It was possible to visit the new quarry and examine the extracted sand.
                                                                                                           The sand dug in the old forbidden pit – a deposit of marine sand – is different from
                                                                                                           the sand excavated today in the new quarry, a river deposit. This sand is grey and
                                                                                                           composed of silica and quartz granules. The study of this material and the extraction
M. Berti - Ibo island in the Quirimbas archipelago: an architectural heritage within a natural heritage




                                                                                                           site is important in understanding how the mortar mixtures were prepared, as well as
                                                                                                           learning more about the presence of underground fresh water at depth and the soil
                                                                                                           itself. A river sand deposit on a coral limestone island is a great advantage but, as
                                                                                                           in the case of the limestone supply, sand removal must be controlled by the public
                                                                                                           administration even for small quantities.

                                                                                                              3.1.6. The impenetrable mangrove forest
                                                                                                              There are two main ways to enter the Ibo mangrove forest, the perimeter of the
                                                                                                           forest and the Caminho dos Senhores artificial channel. Existing pedestrian paths
                                                                                                           suggest that there is a local habit of accessing the mangroves from the island itself
                                                                                                           for the exploitation of mangrove timber for carpentry, construction and so on. The
                                                                                                           conditions of Caminho dos Senhores (about 3 km) can be evaluated in terms of tour-
                                                                                                           ism or local communications with the island of Quirimba. The intrusive trees growing
                                                                                                           along the channel, which are cut during its maintenance, could be used to feed the
                                                                                                           lime kilns and the timber used for construction.

                                                                                                               3.1.7. The cultivated fields
                                                                                                               The crops — rice, vegetables, and fruits — and their geographic locations on the
                                                                                                           island are of great social and cultural interest. Administrative provisions should pro-
                                                                                                           tect and develop this unique and interesting agricultural production system. There is
                                                                                                           also talk of relaunching the production of Ibo coffee. However, at present it is only a
                                                                                                           hypothesis which would require impact studies on business and on environmental
                                                                                                           compatibility (Figure 4).

                                                                                                               3.1.8. Roads and paths
                                                                                                               The network of roads and paths is the sign that best represents Ibo’s urban and
                                                                                                           environmental culture: a true model of study and application. The entire network of
                                                                                                           permanent paths should be mapped, including those that are no longer used but
                                                                                                           still remembered. Neither should the fishermen’s paths on the coral platform be
                                                                                                           ignored; they are recognizable and viable even when they are submerged by the
                                                                                                           high tide.

                                                                                                              3.1.9. Drinking water and domestic soil pollution
                                                                                                              The collection of existing studies on Ibo and the Quirimbas Island Park, as well
                                                                                                           as the related discussions suggest that knowledge of the hydrogeological conditions
                                                                                                           of the soil and subsoil is a prerequisite for any management plan. Considering that
                                                                                                           on the island there are about 150 non-drinkable water wells, with an average of 10
                                                                                                           meters depth [8] and that the island is part of the continent’s alluvial basin [9], it
                                                                                                           would be useful to check whether pristine waters could be drawn by drilling one or
                                                                                                           two wells in depth: this option would be a convenient alternative to an aqueduct that


                                                                                                     258
brings drinking water from the mainland to the island through the lagoon (Figure 5).
While on the one hand, the traditional practice of collecting seasonal rainwater in the
cisterns remains valid, a 35m or 50m deep well for drinking water could qualify the
town and if placed, for example in the Transitional Area (Figure 3), might determine
a moderate urban density or a better placement of new buildings for public use, such
as schools or markets [10-13]1.




Figure 5. An extended section of the continental margin through Ibo. The hypothesis to be verified
is the presence of a deep layer of fresh water from the mainland to the subsoil of the island.



   In addition to the problem of the pollution of existing wells due to human activities,




                                                                                                           CONSERVATION SCIENCE IN CULTURAL HERITAGE
specific studies on environmental impact are essential to verify contamination between
saltwater and fresh water at various levels of groundwater, during high tide cycles and
during periods of rain.


   3.2. Priorities in the conservation of cultural and natural heritage

   A plan for heritage conservation with such complex relationships between human
and natural values must depend on a long-term program, in which actions are based
on a priority scale, carefully using the scarce donations that are available for funding
and improving strategies to maintain what has already been rehabilitated.
   Being as the process of rehabilitation of the architecture in stone and lime is very
long, the owners of the historical architecture, whether uninhabited or in ruins, are
obliged by the public administration to keep the property free from spontaneous veg-
etation to improve public hygiene and at the same time, preserve the architectural her-
itage. The vegetation that grows between the ruins does not protect them, for example
from the sun or rain, but hides them, thus avoiding a visual inspection of the degrada-
tion: visual inspection is the first step in the procedure to preserve artefacts that are
exposed to all kinds of conditions and climate (Figure 6).
   Between 2006 and 2010, a foreign institutional donor, the United States Agency
for International Development (USAID), funded the “Northern Mozambique Tourism

                                                                                                     259
                                                                                                           Project” during which the perception of priorities in rehabilitation work was slightly im-
                                                                                                           proved. During this period of time, for example, we saw that the demolition of the para-
                                                                                                           pet on the waterfront at the entrance to the town was suspended: unlike in the initial
                                                                                                           project, the operators thought that repairing what already existed was a better option
                                                                                                           than demolition and subsequent re-building, even if of poor design and construction.
                                                                                                           But in general terms, it would perhaps have been more appropriate for the donors to
                                                                                                           have prioritised the consolidation of the western part of the town, where there is an
                                                                                                           ancient phenomenon of erosion that threatens all the buildings on the waterfront.
M. Berti - Ibo island in the Quirimbas archipelago: an architectural heritage within a natural heritage




                                                                                                           Figure 6. Wall in Rua Maria Pia. Observation of the phenomenon of disintegration where the
                                                                                                           different conservation state of the two sides (left and right) is evident and has been caused by the
                                                                                                           use of different plasters and exposure to sunlight.



                                                                                                               Within the same program, another case that showed a wise approach to safe-
                                                                                                           guarding Ibo heritage was seen in the temporary works designed to protect those
                                                                                                           monumental buildings where restoration was particularly expensive or where further
                                                                                                           studies were needed to develop appropriate methods for recovery. One example is
                                                                                                           the Fortim de São Jose, where the architectural project manager spent all the time
                                                                                                           that was needed in developing the right technology to reconstruct the flat roof of one
                                                                                                           of the casemates. During this long waiting time, a temporary roof in galvanized sheet
                                                                                                           was put in place.
                                                                                                               Two interesting consolidation tests of the wall were observed on both sides of the
                                                                                                           Fortim de São José gate (Figure 7). The tests, carried out in 2005, had given a nega-
                                                                                                           tive result: the lime mortar had not hardened, but gradually crumbled into dust at the
                                                                                                           foot of the wall. Performing the tests before the widespread application of the planned
                                                                                                           consolidation technique had been the right choice, as some errors were subsequently
                                                                                                           avoided when work was resumed two years later.

                                                                                                     260
   Through an empirical approach and observing test results, the island’s population
was able to learn about the construction technique used by the ancient Portuguese
settlers and thus understand how it makes extensive use of the natural resources of
their island. Knowledge of the construction system and availability of the building ma-
terials on site are two conditions that seem to guarantee the ordinary maintenance of
the rehabilitated architectural heritage.




Figure 7. Left: consolidation tests on the Fortim de São José gate. Right: detail of the limestone
disintegration in the ruins observed on the Rua Maria Pia.



    3.2.1. Stones
    The explanations given by the inhabitants during the Ibo study visits suggested
where exactly on the island the building stones had been extracted. But only during
the third visit, was it possible to fully understand the meaning of the answers given by
the local pedreiros (builders) to questions during the previous visits, that is, where did




                                                                                                           CONSERVATION SCIENCE IN CULTURAL HERITAGE
the coral stones to build with come from? The vague answer was always the same: em
todo lado (from everywhere).
    Two examples of houses under construction in the popular area (the Informal Area)
near the football field were observed. On these two building sites, the coral rock blocks,
walled up with red earth mixed with water and lime, were extracted inside the perimeter
of the house’s property. Digging only one meter deep into the sandy soil, the limestone
skeletons of ancient coral colonies are readily available. The pieces can therefore be
easily extracted and used in the construction site.
    In Ibo, there is a place called kumáwe (ku = area, mawe = stone) in the regional Kimwani
language. This site is at the highest point of the island, at an altitude of 13 meters above the
current average sea level. Here, traces of the excavations for the extraction of limestone
are still visible. Some appear to be from ancient times, others are more recent. In the court-
yard of some houses it is still extracted for the local market. The limestone kumáwe is very
compact with a uniform matrix, so it can be cut directly into orthogonal profiles to obtain
regular blocks more suitable for the construction of higher-quality houses. It is best used in
the construction of walls with overlapping blocks and can be classified under the term ‘bio-
clastic rock’. There is another type of coral stone used for building which can be classified
under the term ‘bioherm rock’. This last type is a coral conglomerate, which is sometimes
not very cohesive and often contains large pieces of coral skeletons [15].
    Searching for the stone quarry used to build the great fortress of São João Baptista,
a depression in the nearby terrain was thoroughly explored. In historical maps, this

                                                                                                     261
                                                                                                           depression in the soil is called ‘Pántano secco na estiagem’. No clear traces of excava-
                                                                                                           tions have been found, but there is a strong possibility that the depression may have
                                                                                                           been produced by digging for the supply of building materials [2].
                                                                                                              On the contrary, at the Fortim de Santo António clear traces of excavation were
                                                                                                           observed. The sediment in which the military building was found was a compact cal-
                                                                                                           careous coral platform. Regular rock cuts on the north and west sides at the base of
                                                                                                           the building show the compactness and other features of the flattened area. Even
                                                                                                           more evident is the pronounced depression south of the fort, which may be the result
M. Berti - Ibo island in the Quirimbas archipelago: an architectural heritage within a natural heritage




                                                                                                           of excavations to extract building material.

                                                                                                              3.2.2. Lime
                                                                                                              Among the open lime kilns observed, some are cyclically activated, such as the two
                                                                                                           near the Catholic cemetery (Figure 8), while others have been found abandoned, as
                                                                                                           indicated on the 2007-2009 visit map (n.2, Figure 4) on the north-east coast.
                                                                                                              The information collected and the direct testing of this kiln have given evidence of
                                                                                                           an artisan production for the market of Pemba, an important city on the continental
                                                                                                           coast about 100 km South of Ibo. The limestone to be cooked comes from different
                                                                                                           sites of the island and is chosen according to its intended use. A special case is the
                                                                                                           use of lime obtained from the calcination of the shells to whitewash the interior walls
                                                                                                           of the houses, making them more habitable because they reduce the perception of
                                                                                                           humidity in the rooms.
                                                                                                              According to the local producers we interviewed, the best quality mortar for plastering
                                                                                                           the walls is obtained from corals from the coral reef edge, west of the lighthouse. A visual
                                                                                                           inspection revealed that also the sedimentary limestone taken from the kumáwe site and
                                                                                                           around the military barracks near the coconut palms is of excellent quality to produce
                                                                                                           lime. This limestone is very compact and uniform and has the texture of small crystals.




                                                                                                                   Figure 8. The lime kiln in the open air at the entrance to the Catholic cemetery.



                                                                                                              From the first direct evaluation of the sands used on the construction sites, it seemed
                                                                                                           that the granules were silica rather than limestone. Local workers said the material had
                                                                                                           been taken from the island itself.


                                                                                                     262
   Until 2007 the sandpit, excavated among the oldest colonial houses, was still
used for small buildings in the Informal Area, but in 2008, the administration de-
cided to ban sand excavations there because it threatened the stability of the sur-
rounding abandoned houses. This measure was the effect of an emergency that
a programming of urban resources would probably have foreseen and, therefore,
avoided.
   Other existing quarries were enlarged or new ones opened in areas outside the
town for the many restoration yards that have been set up in recent years (Figure
9, left). It is curious to note that the two main ones are found near two cemeter-
ies, a Hindu one to the North and a Muslim one to the South (Figure 9, right). This
could suggest that there was a possible correlation between the excavation for
the tombs and the discovery of river sand which was very suitable for mixing in a
lime mortar.




                                                                                             CONSERVATION SCIENCE IN CULTURAL HERITAGE
                Figure 9. Sand site survey in Ibo. Sandpit n.1 on the map.



   Since it was easy to verify the siliceous or calcareous nature of the sand, three
samples were taken from three different quarries. The test showed that the three
samples were silica sand because they did not produce any chemical reaction dur-
ing the experiment. When in contact with hydrochloric acid (HCl), silica sand stays
in its state of physical integrity. On the contrary, when the calcareus sand comes
in contact with the acid it reacts and releases carbon dioxide (CO2). This simple
experiment shows that the continental sand deposits are found on the island itself
and justifies the whole study when we try to correlate sea levels, coral reefs, and
human settlements.


  4. Conclusion

   The balance between the natural and human heritage on Ibo has been pre-
sented in general terms and as a problem open to discussion. The solution to
this problem seems to be in the hands of the island’s population, indeed, com-
munity participation in the conservation of its heritage began with the preparation
of the Plano de Urbanização da Vila do Ibo, in 2007. Part of the population that

                                                                                       263
                                                                                                           emigrated from the island in recent years, is coming back, but the number and
                                                                                                           type of migrants that returned were not evaluated. Nevertheless, the Plano does
                                                                                                           include areas for urban expansion; however, in order to use the island’s resources
                                                                                                           sparingly and to safeguard the culture of the community, these areas of urban
                                                                                                           expansion should not be used until the existing town is completely rehabilitated
                                                                                                           and occupied.
                                                                                                               The restoration of stone and lime houses in the Formal Area (Figure 3) is more
                                                                                                           problematic than that of the popular traditional houses in the Informal Area (Figure 3).
M. Berti - Ibo island in the Quirimbas archipelago: an architectural heritage within a natural heritage




                                                                                                           In the first case, the community has been offered a choice between restoring or recon-
                                                                                                           structing. The island builders have lost the memory of the old colonial techniques and
                                                                                                           therefore more easily construct new buildings of little architectural value in place of the
                                                                                                           ruins of the colonial houses.
                                                                                                               Local administrators attempt to maintain control over historic buildings and preserve
                                                                                                           them by applying existing regulations but with little success, as many historic houses
                                                                                                           are now in ruins or abandoned.
                                                                                                               Today there are obvious intentions to speculate when negotiations involve the is-
                                                                                                           land’s historic houses. Houses are purchased in ruins, so in some cases the site is kept
                                                                                                           clean, but rehabilitation does not follow. In other cases, it is tourism companies and
                                                                                                           international cooperation projects that have rehabilitated some historic buildings and
                                                                                                           thus contributed to the recovery of old construction techniques and the qualification of
                                                                                                           local workers.
                                                                                                               For the restoration of stone and lime buildings, local materials such as sand
                                                                                                           and limestone are required. At present, the local supply of building materials is
                                                                                                           treated as a normal administrative problem, as indicated by the Plano. It evidently
                                                                                                           provides no protection for the integrity of the island. It would therefore be nec-
                                                                                                           essary to introduce into the Plano a special chapter for the management of the
                                                                                                           natural resources of the island and the continental coast in order to avoid future
                                                                                                           environmental emergencies caused by disordered rehabilitation, deforestation and
                                                                                                           dangerous excavations.


                                                                                                               Notes

                                                                                                           1
                                                                                                                 The extended section between the mainland and the continental edge on a track crossing
                                                                                                                 Ibo, combines data from two maps: the Carta Hidrográfrica da Foz do Rovuma ao Ibo of
                                                                                                                 the Instituto Hidrográfico de Lisboa, 1965 (work copy by courtesy of Patricia Oberreuter)
                                                                                                                 [14] and the Plano Topografico base, hoja 1 e 2, 1997 in the Libro Blanco de los recur-
                                                                                                                 sos naturales de la provincia de Cabo Delgado (Mozambique) – Agencia Española de
                                                                                                                 Cooperacion Internacional – Union Europea (copy at the Faculty of Arquitectura e Plane-
                                                                                                                 amento Físico in Maputo) [12].
                                                                                                                 The hypothesis of the presence of fresh water in deep soil has been discussed with
                                                                                                                 the geographer Patricia Oberreuter Tapies [10] of the National Geological Museum of
                                                                                                                 Maputo. The most important orientation texts, cited in the bibliography, are by Peter
                                                                                                                 John Ramsay [11], Agencia Española de Cooperacion Internacional [12], and Russell
                                                                                                                 Arthurton [13].




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      References

[1]     Berti M., Arif M. (2005) Conservação dos antigos edifícios de pedra coral. Dois
        casos ao longo da costa moçambicana. Maputo: Edições FAPF.
[2]     Berti M., (2016) A heritage of coral stone. Padova: Cooperativa Libraria Editrice
        Università di Padova. ISBN: 9788867875351
[3]     Berti M, (2016) Conservation of Coral Stone Architectural Heritage on the Coast
        of East Africa. In: Comer D. C., Versaci A., Amer M. S. (eds.), Conservation of Ar-
        chitectural Heritage (CAH), Procedia – Social and Behavioral Sciences,Volume
        225,14 July 2016, pp. 47-56. DOI: 10.1016/j.sbspro.2016.06.007
[4]     Butzer K. W., (1984) Archaeology as Human Ecology: Method and Theory for a
        Contextual Approach. New York: Cambridge University Press. [I. ed. 1982. DOI:
        10.1017/CBO9780511558245]
[5]     Bento C. L., (1993) As ilhas de Querimba ou de Cabo Delgado: Situação colo-
        nial, resistência e mudança (1742-1822). Lisboa: Universidade Técnica de Lis-
        boa, vol. I. [consulted from 2006 to 2009 in: http://pesodaregua.com.br/capaein-
        dice.htm]
[6]     Carrilho J., (2005) Ibo: A casa e o tempo. Maputo: Ediçoes FAPF.
[7]     Carrilho J., (2006) Arquitectura e Ambiente: Preexistências, transformações e
        desenvolvimento sustentável. O caso da Ilha do Ibo. PhD diss., Sapienza Uni-
        versity of Rome.
[8]     CEDH. 2008. Plano de Urbanização da Vila do Ibo: Vol. 1 – Inventário e Diagnósti-
        co, Vol. 2 – O Plano e seu Regulamento, Maputo: Governo da Província de Cabo
        Delgado – Direcção Provincial de Coordenação da Acção Ambiental, Universida-
        de Eduardo Mondlane, Centro de Estudos do Desenvolvimento do Habitat.
[9]     Coastal and Environmental Services. (1998) Environmental Impact Assessment
        of the Proposed TiGen Mineral Sands Mine, Zambezia Province, Mozambique.
        Volume 4. Relatório de Impacte Ambiental. Grahamstown: Coastal and Environ-




                                                                                                    CONSERVATION SCIENCE IN CULTURAL HERITAGE
        mental Service.
[10]    Oberreuter P. (2004) A necessidade de proteger os corais do arquipélago das
        Quirimbas em Moçambique. Maputo: Museu Nacional de Geologia of Maputo.
        [typescript consulted in 2007 at the National Museum of Geology in Maputo].
[11]    Ramsay P. J. (1995) 9.000 years of sea-level change along the southern Af-
        rican coastline. Quaternary International 31, pp. 71-75. DOI: 10.1016/1040-
        6182(95)00040-P.
[12]    Gabinete de Estudios Tecnicos de Ingenieria S.A. (1997) Libro Blanco de los re-
        cursos naturales de la provincia de Cabo Delgado (Mozambique): Plano Topo-
        grafico base, hoja 1 e 2. Agencia Española de Cooperacion Internacional – Union
        Europea [copy at the Faculty of Arquitectura e Planeamento Físico in Maputo].
[13]    Arthurton R. (2003) The fringing reef coasts of eastern Africa—present process-
        es in their long-term context. Western Indian Ocean Marine Science Association
        (WIOMSA) 2 (1), pp. 1-13. ISSN: 0856-860X.
[14]    Missão Hidrográfica de Moçambique. (1965) Carta Hidrográfrica da Foz do Ro-
        vuma ao Ibo. Lisboa: Instituto Hidrográfico de Lisboa [work copy by courtesy of
        Patricia Oberreuter – Reimpressão: Fevereiro de 1986].
[15]    Procesi D. (1993) Coral Stone and Lime in the East African Coast, M.A. diss.,
        Centre for Conservation Studies, The Institute of Advanced Architectural Studies,
        University of York. [typescript consulted in 2006 at the ICCROM Library in Rome].


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                                                                                                              Biographical notes

                                                                                                              Maurizio Berti is an architect specialised in architectural restoration work. He
                                                                                                           graduated and trained at the University of Venice and University of Padua. He ob-
                                                                                                           tained his PhD at the Sapienza University of Rome. For thirty years, he worked as
                                                                                                           an architect-restorer in the municipality of Padua. As an adjunct professor, he has
                                                                                                           taught at the Eduardo Mondlane University in Maputo, at the Sapienza University
                                                                                                           of Rome and the Carlo Bo University of Urbino. As an associate professor, he has
M. Berti - Ibo island in the Quirimbas archipelago: an architectural heritage within a natural heritage




                                                                                                           been the dean of the Faculty of Architecture at the Lúrio University, Mozambique. His
                                                                                                           publications concern the preservation of cast-iron architectures, historic fortifications
                                                                                                           and coral stone buildings.


                                                                                                              Summary
                                                                                                              This paper presents the method adopted in the study of Ibo, a small island of
                                                                                                           the Quirimbas Archipelago in northern Mozambique. Ibo is part of a larger study,
                                                                                                           begun in 2004 which is still ongoing. In the first phase, the author’s attention was
                                                                                                           focused on the restoration of the historic architecture built with coral limestone. But
                                                                                                           very soon it became evident that it was necessary to study the context in which
                                                                                                           these coral architectures were built. After a few years of careful observation, it was
                                                                                                           apparent that coral stone architecture is strongly conditioned by the knowledge and
                                                                                                           conservation of the natural environment in which it is built. And in the case of Ibo,
                                                                                                           the beauty of its heritage and its conservation lies in the delicate balance between
                                                                                                           architecture and nature.


                                                                                                               Riassunto
                                                                                                               L’articolo presenta il metodo adottato nello studio di Ibo, una piccola isola dell’arci-
                                                                                                           pelago delle Quirimbas nel Nord del Mozambico. Questo caso è parte di un più ampio
                                                                                                           studio, iniziato nel 2004 e tuttora in corso. In una prima fase, l’attenzione dell’autore si
                                                                                                           concentrò sul restauro dell’architettura coloniale portoghese lungo la costa orientale
                                                                                                           dell’Africa. Ma ben presto, fu necessario studiare il contesto in cui sono state costruite
                                                                                                           queste architetture impiegando il calcare corallino o, in termini più generali, il calcare
                                                                                                           madreporico. Dopo alcuni anni di attente osservazioni, si può dimostrare che l’architet-
                                                                                                           tura costruita con la pietra corallina è fortemente condizionata dalla sua conoscenza e
                                                                                                           la sua conservazione dipende dall’ambiente naturale in cui è stata costruita. Nel caso
                                                                                                           di Ibo, la bellezza del patrimonio e la sua conservazione risiedono nel delicato equili-
                                                                                                           brio tra architettura e natura.




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