Biology Reference
In-Depth Information
intensity of biotic invasions are likely to be increased by global change
(Lodge 1993b;Vitousek et al. 1997).
Global change compounds the evolutionary pressures acting on invad-
ing aliens. Where communities are in disequilibrium, natural selection is
likely to favor plants and animals with short life spans, high dispersal abil-
ities, rapid population growth capacities, opportunistic patterns of
resource use, and high evolutionary adaptability (Barrett 2000). Fragmen-
tation of habitats is likely to favor species with high dispersal and colo-
nization capabilities (Barrett 2000). Thus, increasing numbers of rapidly
evolving alien species are likely to alter the composition and dynamics of
all of the world's ecosystems.
Alien invasions possess the capacity to influence global climatic change
(Mack et al. 2000). For example, the deliberate introduction of African
tropical pasture grasses to the Amazon basin holds the potential to
increase the importance of fire and inhibit the recovery of abandoned
pasture areas to tropical forest. Flammable grasses would thus tend to con-
vert forest areas into grasslands and savannas, with reduced biomass and
transpiration. Such change would exacerbate the problem of atmospheric
carbon dioxide accumulation as well as promote warmer and drier con-
ditions throughout the region (fig. 1.1).
Figure 1.1.
Relationships of forest, grassland, fire, and climate as affected by the
widespread introduction of African pasture grasses to the Amazon basin. The
positive feedbacks from the initial influences of land clearing and introduction of
exotic grasses promote the increased influence of fire, which increases the tendency
for transformation of the landscape from tropical forest to grassland and savanna.
(Reprinted with permission from R. N. Mack, D. Simberloff, W. M. Lonsdale,
H. Evans, M. Clout, and F. A. Bazzaz. 2000. Biotic invasions: causes, epidemiology,
global consequences, and control.
Ecological Applications
10:689-710. © 2000 Eco-
logical Society of America.)
