Why
is this project
important or interesting?
Quantification of world-wide geographic
variation in herbivory, seed predation and density-dependent mortality,
and investigation of potential mechanisms underlying these patterns are
significant contributions in their own right, and will lead to
significant increases in our understanding of global ecosystem dynamics.
This increased understanding could be applied to major questions in
ecology. For example:
1) Why is the world green?
In 1960, Hairston et al. suggested that the predominance of "greenness"
in terrestrial ecosystems indicated that predators and parasitoids were
suppressing herbivores more than herbivores suppress plants. There are
now many competing theories on the determinants of interactions between
plants and animals (Hartley and Jones 1997). The World Herbivory
Project will enable us to test the predictions of these theories across
ecosystems in which ratios of herbivory to primary productivity differ.
2) Why are there so many species in
the tropics?
Many theories have been proposed to explain the latitudinal
gradient in biodiversity. One hypothesis is that the greater intensity
of biological interactions in the tropics allows a greater diversity of
species to coexist. Our data will not address this hypothesis directly,
but will show whether interactions really are more intense closer to
the equator.
3) How might vegetation
dynamics change as a result of climate change?
Unless we understand the mechanisms that underlie latitudinal
gradients in biotic interactions it will be difficult or impossible for
scientists to predict what might happen to ecological communities as
climate zones move polewards under global warming.