Take a hectare of land. Two developers come along with two propositions for how to develop it. You have to decide which is the most sustainable.  How do you do it?

You could start by calculating the ecological footprint of each and comparing them.

The One Planet Development (OPD) Ecological Footprint Calculator is a resource accounting tool that helps cities, regions and countries understand their ecological balance sheet and gives them the data necessary to manage their resources and secure their future.

The unit used is global hectares per capita, that is to say the amount of average quality land area required to provide all the things we need as individuals and absorb the pollution we create as a result.

While it is true that there are concerns[1] about the accuracy of some of the tool’s assumptions, for example the scoring may need tweaking for different types of land-use, there is no denying its general message, and the assumptions are being constantly improved.

The most recent data is from 2010. In that year, the USA had the highest footprint in the world: 8 ha per capita; but it has a biological carrying capacity of 3.9 ha per individual. This gives it a deficit of 4.1 ha per individual. In other words, Americans are using roughly twice as much as they can sustainably manage.

The United Kingdom has an average ecological footprint of 4.9 hectares, with a biocapacity of 1.3 ha. In other words, British citizens are using more than three and a half times they can sustainably manage.

The calculator is a spreadsheet-based tool based on the REAP (Resources and Energy Analysis Programme) 2 tool from the Stockholm Environment Institute. It can be used to evaluate any development proposition.

REAP: helps policy makers to understand and measure the environmental pressures associated with human consumption. It can be used at the local, regional and national levels and generates indicators on

  • Carbon dioxide and greenhouse gas emissions measured in tonnes per capita.
  • The Ecological Footprint required to sustain an area in global hectares per capita
  • The Material Flows of products and services through an area measured in thousands of tonnes.

Current users include local, regional and national governments in the UK, commercial users, academic users, and NGOs.

The Welsh government is one of the first in the world to use the calculator in its mission to attain its policy aim of reaching One Planet Wales. Applicants wishing to build housing and practice horticulture on greenfield land must satisfy planners that they reach a certain level of ecological footprint by using a similar calculator

Lammas (seen in the model below) is a development on greenfield land in Pembrokeshire, Wales, approved under Clause 52 of the local authority's planning guidance, later subsumed into the Welsh government's One Planet Development policy.


Map of Lammas

The Ecological Footprint Calculator uses mostly financial information to lay out consumption - whether from a household, a development proposition or a city or anything in between - over the year and allocate environmental impacts to it.

Results are generated in global hectares (gha) per capita. It takes into account expenditure on energy use, housing, infrastructure travel and transportation, food purchased, food produced on site for home use, and other goods and services purchased.

So it could tell you whether a self-sufficient smallholding on greenbelt land 20 miles outside the city boundaries but needing eight journeys per day would be more sustainable than an apartment block on a brownfield site within the city.

The tool even recognises that the administration of public services carries environmental impacts that are shared by all citizens and these are included and are assumed to be 50% of the household's ecological footprint.

If it were used across-the-board we would have an easy and transparent way of comparing the impacts of any development application for land use conversion.

England and Wales

Conditions for granting planning permission for one planet living-style development on rural land are granted under what is known as a section 106 agreement. Section 106 (known as s106) of the Town and Country Planning Act 1990 enables a development proposal to become acceptable in planning terms, by attaching certain conditions.

For example if a supermarket chain wants to build on the edge of town, conditions might include the provision of a new road or facilities for the school, which saves the local authority from having to pay for it out of taxpayers money.

Amongst the s106 conditions imposed under the now defunct Clause 52 in Pembrokeshire, Wales (which governs Lammas), was that occupants of low impact developments must obtain at least 75% of their livelihood from the land around their dwelling, and be limited to 8 trips per day in a vehicle.

The Technical Advice Note (TAN) 6 condition introduced in 2011 in Wales that uses the ecological footprint calculator to approve One Planet Development applications is only a slight improvement, bringing this down to either 65% of all subsistence, or 30% of food and 35% of livelihood coming from the land.

Hockerton Housing Project

Contrast this with a s106 requirement in Nottinghamshire, England, for the residents of Hockerton Housing Project (above) in 1994. There, instead of a percentage of income, a fixed number of unpaid hours (300 per year per household) must be spent on the land and in addition 300 paid hours per year supporting the joint business which runs tours and educational events, hosts away-days and consulting on both new and retrofit energy efficient building.

Given that a standard working year consists of 1,650 hours, this leaves 64% of the working year available to do anything else.

All of these conditions were designed to ensure that the occupants of these houses gained most of the employment and subsistence from the land and were not going to commute daily to a nearby town to work. There are also conditions under which they are not allowed to sell to anybody else who would also commute and not make the land productive.

The Hockeerton arrangement seems to me to be fairer, more achievable and manageable. 

Th Clause 52 condition will be seen as the most extreme to be attached to permitted low impact development, one that is highly restricting given the vagaries of the weather. 2012 was particularly bad all over the UK and anyone relying to a large extent on their own cultivation for the majority of the subsistence found it incredibly tough.

On car use, the Clause 52 requirement for vehicle trips to be curtailed in number to eight per day (inward or outward) was irrational since the trips may be of any length. The TAN 6 stipulation on transport restrictions is an improvement. The guidance for transport says:

"Planning applications should be accompanied by an assessment of the traffic generated from the use of the site by its residents and visitors. The travel plan accompanying the planning application should clearly identify a preference for low or zero carbon modes of transport including walking, cycling and car sharing schemes. Where proposals are distant from larger towns and villages they should be located near public transport routes to minimise use of the private car."

Taken sensibly this should certainly help to facilitate low impact developments such as they can be further mainstreamed.

The worry is that the political attention has now shifted away from one planet development and towards affordable housing in Wales, and towards deregulation in England. Unless there is a concerted effort to pursue the advantages, and there are many, of low impact development backed up by robust evidence, especially since it can provide affordable housing, it's yet possible that Wales' experiment could be seen in the future as an aberrant cul-de-sac.

It would be tragic were this to be the case.

[1] Measuring sustainability: Why the ecological footprint is bad economics and bad environmental science, Nathan Fiala1, Ecological Economics Volume 67, Issue 4, 1, pp519–525, Elsevier, November 2008