Fresh water is vital to human life and economic wellbeing,
and societies draw heavily on rivers, lakes, wetlands,
and underground aquifers to supply water for drinking,
irrigating crops, and running industrial processes. The benefits
of these extractive uses of fresh water have traditionally
overshadowed the equally vital benefits of water that remains
in stream to sustain healthy aquatic
ecosystems. There is growing recognition
that functionally intact and biologically
complex freshwater ecosystems provide
many economically valuable commodities
and services to society (Figure 1). The
services supplied by freshwater
ecosystems include flood control,
transportation, recreation, purification of
human and industrial wastes, habitat for
plants and animals, and production of fish
and other foods and marketable goods.
These human benefits are what ecologists
call ecological services, defined as “the
conditions and processes through which
natural ecosystems, and the species that
make them up, sustain and fulfill human
life.” Over the long term, healthy freshwater
ecosystems are likely to retain the adaptive
capacity to sustain production of these ecological services in the
face of future environmental disruptions such as climate change.