Each organism on earth lives in a complex relationship with scores of other organisms, and its survival depends on the quality of its environment. A community of all living organisms (animals, plants and micro-organisms), interconnected with their biotic and abiotic environment, is called an ecosystem. Ecology is the science concerned with the protection of ecosystems.

In the past few decades, ecosystems have suffered increasing damage due to human interventions such as deforestation, urbanisation, extraction of raw materials, and so on. This evolution has far-reaching consequences for the earth's biodiversity: for example, if we keep on cutting down the tropical forests at the current rate, then within 30 years 5 to 10 % of all natural species will have become extinct. Human beings have a very direct interest in maintaining biodiversity : just think of the wild ancestors of cultivated crops with desired characteristics such as disease resistance, or of valuable medicinal plants yet undiscovered in the rain forest.

Scores of organisations are battling to preserve biodiversity (WWF, IUCN,…), and governments in many countries have undertaken, inter alia via ratification of the Rio Conference, to develop a sustainable development policy.

Satellite images form an important instrument for studying and protecting ecologically valuable areas such as tropical forests and river deltas.

A first step in this effort is to carefully map such areas.
By monitoring them in time and space, one can identify the factors which threaten ecosystems. At the same time, models can be developed which make it possible not only to extrapolate recent evolutions into the future, but also to evaluate what the impact of specific policy options will be. Satellite images thus indirectly offer valuable information which should encourage policymakers to intervene in time and, if necessary, to actively protect specific areas.