UNSW Sydney scientists have revealed that excessive grazing by kangaroos in arid regions of Australia can alter the food web between dead vegetation, termites, and animals that depend on termites for food. The findings, published in the journal Ecosystems, show that overgrazing by kangaroos in arid ecosystems can hinder the consumption of dead vegetation by detritivores like termites and earthworms. The research has important consequences for preserving biodiversity in Australia’s arid areas.
Scientists at UNSW Sydney have conducted research on the impact of overgrazing by herbivores, such as kangaroos, on arid ecosystems in Australia. This research has shown that overgrazing can lead to a reduction in termites, which serve as the primary decomposers in these environments. The reduction in termites can then have a cascading effect, resulting in a decline in the number of small vertebrates like lizards, desert frogs, and dunnarts that feed on termites.
Green and brown food webs
The focus of this research was on “brown food webs,” which are based on the consumption of dead or decaying vegetation by detritivores, like termites or earthworms. Most food web research has been conducted on “green food webs,” which begin with the consumption of living vegetation by herbivores.
The research took place at Boolcoomatta Station Reserve, a conservation reserve managed by Bush Heritage Australia. The area is inside the dingo fence in South Australia, where sheep grazing is the predominant land use and the dingo, a top predator, is “functionally extinct.” Kangaroos occur in large numbers in this region due to the suppression of the dingo population and the availability of artificial water sources.
Biodiversity Implications for all Arid Regions in Australia
The researchers compared the cover of living and dead vegetation, the abundance of detritivorous termites, and their predators inside enclosures where kangaroos were excluded to nearby control plots. They found that the exclosures, with kangaroos absent, had a higher cover of living and dead vegetation and more termites and small vertebrates that feed on termites.
This research highlights the importance of considering brown food webs in the conservation of biodiversity in arid ecosystems. By preserving the dead vegetation that serves as a food source for detritivores and small vertebrates, we can maintain the health of the desert food web and protect the important role these small species play in supporting the larger animal populations in the ecosystem.
“Our findings are one of the first to show in arid ecosystems that where herbivores were excluded, there was greater biomass of dead grass. In turn, there were more termites and predators of termites inside the exclosures,” says lead author Baptiste Wijas. “These small vertebrates are an essential component of biodiversity in desert environments and play a crucial role in desert food webs by being prey for larger animals such as larger marsupials, birds of prey, snakes, and goannas.”
The new study has crucial implications for preserving biodiversity in arid regions of Australia, says Prof. Letnic. The findings provide insight into the impact of grazing on arid ecosystems, allowing for informed decisions on herbivore population management. Conservationists can use the information to detect early signs of habitat disturbance that is vital for safeguarding other species.
