Biodiversity of Freshwaters - Freshwater Ecology: Concepts and Environmental Applications - page 199

Many endangered species are aquatic or require aquatic habitat. In
1999, the U.S. Fish and Wildlife Service listed hundreds of aquatic species
on their threatened and endangered list, including 73 fishes, 69 bivalves,
28 snails, 17 amphibians, and 20 crustaceans. In addition, mammals and
birds that require aquatic habitat are listed, such as the whooping crane
(Grus americanus), the Florida panther ( Puma concolor coryi; the only re-
maining habitat for this animal is wetland), and the bald eagle (Haliaeetus
leucocephalus). Globally, the IUCN (World Conservation Union) lists 1151
recognized, endangered, freshwater invertebrates. Many more may be en-
dangered, but because they are inconspicuous they have not been listed
(Strayer, 2001). Many wetland plants, particularly those associated with
the vernal pools of California, are also listed as endangered and threatened.
About half of all the crayfish species in United States and Canada are
threatened. Pressures on native crayfish include habitat destruction, limited
natural ranges, and introduced competitors (Taylor et al., 1996).
Just because a group of species is not listed does not mean that no
species in the group are threatened with extinction. We know much less
about the small organisms than the large organisms. New species of aquatic
insects, protozoa, algae, and bacteria are described daily, whereas new
species of mammals and plants are described more rarely. It is clear that
pollution, dewatering, and habitat destruction have negative effects on all
freshwater organisms from fish to bacteria. Thus, small organisms may not
be listed as endangered simply because their existence or the state of their
population in nature is not known.
Many species have been extirpated (locally extinct). For example, of the
44 species of unionid mussels ever found in Kansas, 4 are extinct and 6 en-
dangered statewide. An additional 16 are listed as threatened (Obermeyer et
al., 1997). Not all these species are rare or extinct in other parts of their his-
torical range. The numbers of extinct, endangered, and threatened mussel
species are similar in all states throughout the Mississippi drainage. Between
34 and 71% of the mussel species found in the southeastern United States
are threatened or endangered. Thirty-six species that are thought to be ex-
tinct in the United States were found in the Tennessee River basin alone
(Neves et al., 1997). Likewise, some western states have high proportions of
threatened endemic species. For example, in the Great Basin, Klamath and
Sacramento basins, 58% of the native fishes are endemic. Essentially all the
native fish species are threatened in Nevada (Warren and Burr, 1994).
WHAT IS THE VALUE OF FRESHWATER SPECIES DIVERSITY?
Microbial processing of human wastes has been estimated to be worth
more than $700 billion per year worldwide, and bioremediation of haz-
ardous waste will save 85% of the costs over nonbiological methods of
treatment (estimated at $135 billion worldwide over the next 30 years;
Hunter-Cevera, 1998). The economic benefits of fisheries were discussed in
Chapter 1. Biodiversity may be important to the aquaculture industry. Di-
versity provides genetic diversity and animals and plants for culture. Diver-
sity is also important because of the reliance of aquaculture systems on
healthy biological systems (Beveridge et al., 1994). Another argument for
concern over extinction is that the species we live with are analogous to