preservation of biodiversity requires intricate knowledge of the patterns and
processes that affect ecosystem function. The tropics, particularly tropical
forests, are expansive biodiversity reservoirs (Stevens 1989). Many species in
the tropics are limited in distribution, and the spatial turnover of species is
high among many taxonomic groups (Condit et al. 2002). Species distribu-
tion patterns are not uniform across the globe; most groups of organisms show
a strong increase in species richness, or number of species per unit area, nearer
to the equator. Additionally, the number of species in most terrestrial and
freshwater groups is greater at lower than at higher elevations and greater in
forests than in deserts (Gaston 2000). These general patterns suggest that
tropical environments are favorable to the evolution of new species and the
persistence of existing species. High diversity in the tropics is generally attrib-
uted to high productivity, low environmental variance (e.g., seasonality), per-
sistent predation and competition, lower historical climatic change impacts,
and differential speciation and extinction rates. Recognizing that these attrib-
utes tend to support high diversity in the tropics, it is important to note that
there are significant intratropical diversity patterns and that lower-diversity
regions can also be found in the tropics.
Conservation efforts have focused much attention on tropical forests
because they are the richest strongholds of terrestrial biodiversity. Therefore,
exploitation of natural resources in the tropics results in the destruction of
large genetic reservoirs. Incalculable benefits are gained from maintaining
species numbers and the current diversity of organisms. Much of the research
on ecological and evolutionary benefits is new, and more research must be
conducted to determine broad patterns and processes. Research has shown
that on local scales, the lower the species diversity within a system, the more
vulnerable it is to species and population extinctions as a result of nonnative
species invasions (Levine 2000). One can conclude that the maintenance of
high diversity could reduce the number of invading species, thereby greatly
reducing the negative impacts of these species (Kennedy et al. 2002). Other
biodiversity effects on ecosystem processes have also been demonstrated
(Cardinale et al. 2002). For example, plant diversity of European grasslands
positively influences plant primary production (Loreau and Hector 2001).
Additionally, diverse areas tend not only to have more functional components
(more species with diverse ecologies) but also to maintain more predictable
ecological processes (McGrady-Steed et al. 1997).
Unfortunately, short-term economic gains driven by increasing human
populations usually influence the decision-making process that leads to
resource overuse. High population growth rates in tropical countries create
socioeconomic difficulties. Environmental constraints, such as climate, often
compound prevalent problems such as malnutrition and famine. This situa-
tion, combined with the need of tropical countries to rely on more advanced
countries for technical assistance and for the development of their own
18 I. Conservation Biology and Landscape Ecology in the Tropics