Persistent global warming could bring down herbivore populations

Herbivore populations will go down as temperatures go up, causing large shifts in food chains with consequences for global food security and species conservation, Canadian researchers have warned.

A team of ecologists says that differences in the general responses of plants and herbivores to temperature change produces predictable declines in herbivore populations.

This decrease occurs because herbivores grow more quickly at high temperatures than plants do, and as a result the herbivores run out of food.

“If warmer temperatures decrease zooplankton in the ocean, as predicted by our study, this will ultimately lead to less food for fish and less seafood for humans,” says co-author Benjamin Gilbert of U of T’s ecology and evolutionary biology department.

Several studies have shown how the metabolic rates of plants or animals change with temperature. Gilbert and his colleagues incorporated these rates into commonly-used, mathematical models of plants and herbivores to predict how the abundance of each should change with warming.

They confirmed their predictions in an experimental study in which phytoplankton and zooplankton populations in tanks of water shifted significantly with changes in water temperature.

Gilbert cautions that long-term tests are required.

The study will be published in the journal in American Naturalist.