Story at a glance

  • Following a major heat wave that damaged the seagrass meadows of Shark Bay, Australia, researchers modeled how a lack of tiger sharks would affect the ecosystem.
  • The results suggest that increased herbivore feeding from a lack of predation exacerbates ecosystem degradation.

The destruction and endangerment of natural habitats and ecosystems is widely synonymous with deforestation, severe weather patterns and species endangerment and extinction. 

A new study posits that habitat degradation could be exacerbated by the extinction of a certain category of species: predators.

Published in the Journal of Animal Ecology, university researchers worked to determine if the loss of apex predators in various ecosystems has an effect on how a given ecosystem responds to an extreme weather event, or how these ecosystems are poised to otherwise suffer from climate change without the presence of natural predators.


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To test this theory, researchers monitored tiger sharks in Australia’s Shark Bay and how the fluctuations in local shark populations changed the seagrass meadows native to the location. 

The seagrass in Shark Bay is the primary food source for sirenians (sea cows) and sea turtles native to the ecosystem. It is also threatened by extreme weather events that are potentially associated with anthropomorphic climate change, most recently a 2011 heat wave caused by strong La Niña conditions. 

This caused “catastrophic” damage to the seagrass meadows in the bay, forcing sirenians and turtles from the area to find other sources of food. 

These conditions were ideal for researchers to simulate how sirenian feeding habits can hinder recovery of biomass threatened by severe climate events, as well as how a lack of natural predators can contribute to the devastation of the ecosystem. 

Knowing that tiger sharks routinely feed on sirenians and other large aquatic herbivores, the study authors wanted to see how the seagrass ecosystem could be further disrupted when the region’s major predator is absent.

After simulating sirenian grazing habits, researchers found that seagrass meadow coverage declined quickly with an abundance of marine herbivores foraging for food, implying that without tiger sharks to mitigate the population, seagrass coverage dwindles at a faster rate. 

“Our results suggest that changes to herbivore behaviours triggered by loss of predation risk can undermine ecological resilience to [extreme climactic events], particularly where long‐lived herbivores are abundant,” the report concluded. 

While both climate change events and loss of predatory species can each amplify the loss of natural habitats, the methods for managing them differ. Researchers recommend that local and regional management is critical to preventing widespread ecological damage.

The reforestation and conservation of apex predators in these ecosystems is also a short-term method to further mitigate damage to an ecosystem. 


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Published on Mar 22, 2021