Ecosystems represent intricate, delicate networks that are fundamental to life on Earth. They furnish us with sustenance, water, and pure air while playing a vital role in climate regulation. Regrettably, human activities such as pollution, deforestation, and climate change have left many ecosystems vulnerable to degradation.
A promising strategy for rejuvenating these fragile systems involves the reintroduction of natural predators and native species. Natural predators help maintain balance by preying on other animals, often keeping invasive species in check. Meanwhile, native species, both flora and fauna, can restore an ecosystem's equilibrium. Below I outline a number of case studies that illustrate the efficacy of utilising natural predators and native species for ecosystem recovery:
At the Great Barrier Reef, scientists have deployed red crabs to combat the destructive crown-of-thorns starfish. By bolstering the red crab population, a natural predator of the starfish, researchers aim to safeguard the vulnerable coral ecosystem.
In the United States, grass carp are being introduced to control invasive aquatic plants that can displace native species and harm infrastructure, such as dams and irrigation systems. Grass carp, native to the region, are known for their ability to consume invasive plants, thus benefiting the environment.
The Scottish Highlands have seen the reintroduction of Soay sheep, which are native to the area and renowned for grazing on invasive plants. Their presence helps curb plant overgrowth, thereby preserving the delicate Highland ecosystem.
In Australia, the blue-tongue lizard is being employed to control the invasive cane toad population. As a natural predator of the toad, increasing the blue-tongue lizard population aims to counteract the cane toad's detrimental effects on native species.
The United States has also turned to barn owls to manage rodent populations, which can damage crops, spread diseases, and threaten native wildlife. As a natural predator of rodents, increasing barn owl populations can protect the environment.
These examples represent just a small fraction of the initiatives leveraging natural predators and native species to restore ecosystems worldwide. However, as we have often heard, it is essential that such reintroduction or recovery programs are properly assessed in terms of feasibility and, in particular, with respect to potential unintended consequences. Each of these examples has some form of risk associated with it due to the fine balance of processes within ecosystems. The often-quoted example of the cane toad provides a stark warning. First introduced in Australia in the 1930s as a means of controlling sugar cane pests, the cane toad quickly became an invasive species itself, wreaking havoc on native wildlife and ecosystems. This cautionary tale underscores the importance of conducting thorough risk assessments, evaluating the potential impacts on native species and ecosystems, and carefully monitoring the outcomes of such interventions to ensure their long-term success and prevent any adverse effects on the delicate balance of nature.
Further reading:
Courchamp, F., Fournier, A., Bellard, C., Bertelsmeier, C., Bonnaud, E., Jeschke, J. M., & Russell, J. C. (2017). Invasion biology: Specific problems and possible solutions. Trends in Ecology & Evolution, 32(1), 13-22.
Estes, J. A., Terborgh, J., Brashares, J. S., Power, M. E., Berger, J., Bond, W. J., ... & Wardle, D. A. (2011). Trophic downgrading of planet Earth. Science, 333(6040), 301-306.
Kumschick, S., Bacher, S., Dawson, W., Heikkilä, J., Sendek, A., Pluess, T., ... & Essl, F. (2012). A conceptual framework for prioritization of invasive alien species for management according to their impact. NeoBiota, 15, 69-100.
Ripple, W. J., & Beschta, R. L. (2012). Trophic cascades in Yellowstone: The first 15 years after wolf reintroduction. Biological Conservation, 145(1), 205-213.
Ritchie, E. G., & Johnson, C. N. (2009). Predator interactions, mesopredator release and biodiversity conservation. Ecology Letters, 12(9), 982-998.
Seddon, P. J., Griffiths, C. J., Soorae, P. S., & Armstrong, D. P. (2014). Reversing defaunation: Restoring species in a changing world. Science, 345(6195), 406-412.
Wallach, A. D., Johnson, C. N., Ritchie, E. G., & O'Neill, A. J. (2010). Predator control promotes invasive dominated ecological states. Ecology Letters, 13(8), 1008-1018.