Most species have adapted to specific habitats that meet certain temperature, rainfall, soil, and vegetation requirements. When a habitat is lost or degraded, many organisms cannot simply move or migrate to another — they must adjust to the changes or die.
Throughout the world, natural habitats are on the decline, primarily because people are converting them to other purposes. Individuals, corporations, and governments are draining and filling wetlands, cutting down forests, and building over savannahs for development and agriculture. As the human population — and per capita consumption — have increased, so has the amount of land devoted to shopping malls, housing developments, office complexes, and urban areas, as well as to agriculture. Each year, millions of acres of natural habitat are being converted to human uses (Devitt, 2005).
Even when habitats are not completely destroyed, various human activities can degrade them significantly. For example, roads, power lines, and other structures break forests and other habitats into isolated patches; this "fragmentation" disrupts animal migration, breeding, seed dispersal, and pollination — and threatens organisms’ survival. Chemicals and debris that run off farms, lawns, construction sites, and landfills end up in the ocean, causing huge "dead zones" where fish cannot live (UNEP).
People depend on natural ecosystems for many goods and services — including regulating climate, filtering water, soil formation, and plants and animals. One study described in Science magazine evaluated these goods and services and estimated that converting natural habitats to other uses costs the world about $250 billion each year in net economic value (commondreams.org). It found the benefit-to-cost ratio to be more than 100 to one in favor of preserving habitats.
David Brower spoke of what he called "global CPR" — conservation, preservation, and restoration. All three may be necessary, depending on the setting, and all have a place in schooling for sustainability. Restoration of damaged habitats, in particular, can be a powerful and rewarding activity for students.
References cited in this article may be found in "References" in the Resources part of our website.
