
Term Term description
Haber-Bosch process

An industrial method of directly synthesizing ammonia (NH3) from hydrogen (H+) and nitrogen (N2), developed by the German chemists Fritz Haber and Carl Bosch. This has led to an annual doubling of the amount of atmospheric nitrogen that is fixed and made biologically available, in turn having significant impacts on ecosystem processes.



habitat fragmentation

When a habitat is broken into several smaller section by human activities and construction (e.g. roads, agriculture, cities) the organisms are confined to smaller areas of land with fewer resources. Fragmented habitats greatly impede animal migrating patterns.

Hadley Cells

Circulation patterns of atmospheric convection currents as they sink and rise in several intermediate bands. Also referred to as Trade Winds.

Hadley cells

Circulation patterns of atmospheric convection currents that are strongest and most well defined at the equator. These circulating cells of atmosphere carry equatorial hat toward the north and south poles.

heat engine

An engine that converts heat energy into mechanical energy.

heat sink

Any environmental landscape or medium that absorbs heat is a heat sink. For example, forests and oceans can absorb heat better that a city landscape.

heavy soils

Soils with a high percentage of small clay particles and characterized by slow water infiltration into the soil, slow water percolation through the soil, low soil aeration, and a tendency for the soil to hold moisture with great tension.


A unit of area in the metric system that is equal to 10,000 square meters or 2.47 acres.


Personification of the Sun in Greek mythology.

Henry's Law

Henry's Law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. For example, the amount of CO2 that is dissolved in the earth's oceans is directly proportional to the concentration of CO2 in the atmosphere directly over the oceans. As [CO2] in the atmosphere increases, so does the [CO2] dissolved in the ocean water which causes ocean acidification.


A substance that is toxic to plants and is used to destroy unwanted vegetation.


An animal that feeds mainly (or only) on plants.



high yield crop



In Islam, an area set aside for the conservation of nature, typically including fields, wildlife, and forests.


An ancient  and diverse religious and cultural tradition of Southeast Asia, characterized by the belief in reincarnation, one absolute being of multiple manifestations, the law of cause and effect, following the path of righteousness, and the desire for liberation from the cycle of births and deaths.

holy water

In Christianity, water that has been blessed by a priest or other religious leader and used in religious practices and ceremonies.



The tendency of an organism or cell to regulate the chemical processes that take place internally so as to maintain health and functioning, regardless of outside conditions. The ability to maintain a steady body temperature is an example of homeostasis.


An expert in the science of cultivating plants (fruit or flowers or vegetables or ornamental plants).

human dignity

The moral quality of human personhood by virtue of one's body, mind and soul, and expressed in human autonomy, equality, freedom, sociality and sacrality.

human rights

Moral powers of human personhood by virtue of human dignity that call for a person or group’s immunity from unjust harm (e.g. the right not to have my bodily integrity abused, the right not to have my expression of ideas suppressed, the right not to have my practice of religion forbidden) and entitlement to basic goods necessary for life (e.g. my right to food, my right to shelter, my right to health care).


When a person demonstrates humble traits such as mildness, modesty, patience and deference.




The act of mixing different species or varieties of animals or plants and thus to produce hybrids (the offspring of genetically dissimilar parents/stock.

hydraulic fracturing

(fracking) A controversial process of natural gas extraction, where millions of gallons of water, sand and chemicals are pumped underground to break apart the rock and release the natural gas for use as an energy source.


Chemical made up of carbon and hydrogen that are found in raw materials such as petroleum, coals and natural gas, and derived products such as plastics.

hydrogen bond

A chemical bond connecting a hydrogen atom of one molecule to an electro--negatively charged atom, especially a nitrogen, oxygen, or fluorine on another molecule.

hydrologic cycle

The natural cyclic transfer of water vapor from the Earth's surface via evaporation into the atmosphere, from the atmosphere via precipitation back to earth, and through runoff into streams, rivers, and lakes, and ultimately into ground water and the oceans.

hydrologic cycle



Water-loving. In Chemistry, a term applied to polar molecules that can form a hydrogen bond with water.


Water-fearing. In Chemistry, a term applied to nonpolar molecules that cannot bond with water.


All of the Earth’s water; this would include water found in the sea, streams, lakes and other waterbodies, the soil, groundwater, and in the air.

hydrothermal vents

A fissure on the floor of a sea out of which flows water that has been heated by underlying magma. The water can be as hot as 400°C (752°F) and usually contains dissolved minerals that precipitate upon contact with the colder seawater, building a stack of minerals, or chimney. Hydrothermal vents form an ecosystem for microbes and animals, such as tubeworms, giant clams, and blind shrimp that can withstand the hostile environment.


Any of the threadlike filaments produced by certain bacteria.

hyporheic zone

A region beneath and alongside a stream bed, where there is mixing of shallow groundwater and surface water.


A supposition or proposed explanation of a phenomenon made on the basis of limited evidence as a starting point for further investigation.


Inadequate levels of oxygen for survival, particularly in aquatic, marine and soil environments.
