dam

A structure that blocks the flow of water in a river or stream. (Chapter 14)

debt-for-nature-swaps

Arrangements in which a wealthy nation forgives the debt of a developing nation in return for a pledge to protect natural areas in that developing nation. (Chapter 13)

decomposers

Organisms such as bacteria and fungi that break organic matter all the way down to constituent atoms or molecules in a form that plants can take back up. (Chapter 10)

demographic factors

Population characteristics such as birth rate or life expectancy that influence how a population changes in size and composition. (Chapter 4)

demographic transition

A theoretical model that describes the expected drop in once-high population growth rates as economic conditions improve the quality of life in a population. (Chapter 4)

density-dependent factors

Factors, such as predation or disease, whose impact on a population increases as population size goes up. (Chapter 9)

density-independent factors

Factors, such as a storm or an avalanche, whose impact on a population is not related to population size. (Chapter 9)

dependent variable

The variable in an experiment that is evaluated to see if it changes due to the conditions of the experiment. (Chapter 2)

desalination

The removal of salt and minerals from seawater to make it suitable for consumption. (Chapter 14)

detritivores

Consumers (including worms, insects, crabs, etc.) that eat dead organic material. (Chapter 10)

discounting future value

Giving more weight to short-term benefits and costs than to long-term ones. (Chapter 6)

dissolved oxygen (DO)

The amount of oxygen in the water. (Chapter 15)

dose-response curve

A graph of the effects of a substance at different concentrations or levels of exposures. (Chapter 3)