"Animals, considered as a dynamic factor of the biosphere,
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The research paper in PNAS by Harvey et al. explains the significance of their results, with some surprising numbers:
The title, “Global diversity and energy of animals shaping the Earth’s surface,” leads us to think of the many ways that “ecosystem engineers” large and small are at work in this essential role.
"Animals profoundly influence Earth surface processes and landforms, but their collective significance has not been quantified. Integrating data across freshwater and terrestrial ecosystems, we uncovered over 600 animals with reported geomorphic effects, including five livestock taxa.
Many more are doubtless overlooked due to inherent geographical and taxonomic biases in published research. We conservatively estimate that wild animal species collectively contribute ≈76,000 GJ energy or more to geomorphic processes annually, equivalent to the energy expended by hundreds of thousands of extreme floods. Livestock acting as geomorphic agents are estimated to exceed this contribution by three orders of magnitude. Our results reveal that the energy of animal geomorphic agents is a significant and overlooked driver of landscape change at the global level."
The title, “Global diversity and energy of animals shaping the Earth’s surface,” leads us to think of the many ways that “ecosystem engineers” large and small are at work in this essential role.
"Animals cause landform change both directly, by mixing soils and sediments (bioturbation) and via the displacement of Earth materials (bioerosion and bioconstruction), and indirectly, by conditioning rock, soil, and sediment particles to be more or less susceptible to erosion and transport by geophysical processes. For example, riverbed gravels can become less mobile when bound by caddisfly silk or more mobile when disturbed by benthivorous feeding fish."
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