“North Island Brown Kiwi”, Photograph by Maungatautari Ecological Island Trust, at Wikipedia distributed under CC-BY-SA-2.5 license (https://commons.wikimedia.org/wiki/Category_talk:Illustrations_from_the_Maungatautari_Ecological_Island_Trust )
Think tourism brings wealth and prosperity to local inhabitants? Not these foreigners- non-native mammals are actually the number one cause of extinction for native island animal species.
Erin E. McCreless and other researchers from the University of California Santa Cruz recently published a study in Nature Communications investigating the inner workings of this important issue. Their study described a new method of analyzing species extinction risk, where island climate and invasive species type are factored into the extinction risk for affected native species.
Stated by McCreless in a Science Daily article that referenced the paper, “We were able to estimate that up to 45 percent of globally threatened vertebrate populations on islands may be extirpated in the absence of conservation interventions, but that targeted invasive mammal control and eradication could prevent 41 to 75 percent of these predicted future extirpations… That is critical knowledge for both conservationists and funders.” This quote supports long-understood concepts about invasive species. It is common knowledge that invasive species like rats, cats, pigs, and mongooses destroy fragile native populations and deeply impact the local ecosystems of their island habitats, but researchers have only recently started to explore their differing impacts on native species.
In the past, researchers mainly based conservation programs on first-hand experience and conventional wisdom, which left a large gap in the scientific backing of the effectiveness of their programs and decision-making for future projects.
In the study, researchers analyzed global patterns of island vertebrate species extinction from a collaborative, global archive called the Threatened Island Biodiversity Database. This database allowed them to compile data points from over 1,200 threatened and extinct island species from over 1,000 different islands. With this data, they were then able to develop models that will allow researchers to better predict and judge which species on which islands are at the most risk of extinction.
From these models, researchers can figure out which conservation interventions would make the most significant difference for the greatest number of at-risk species. This comes into play because of how the varying sizes and climates of the different islands interact with the varying body sizes and characteristics of the island species and their invasive predators. For example, removing a specific invasive species might impact a native species greatly on a small island, but then be an ineffective intervention on a larger island. Additionally, the removal of that invasive species might impact other native species in varying ways. In the Science Daily article referencing the published study, coauthor Donal Croll stated that, “This kind of information is critical for conservationists trying to decide where to spend limited funds”, a dilemma that can make the difference of extinction and recovery for threatened species.
Despite this, some argue that the spread of “invasive species” is a natural process of dispersal, and that the resulting extinctions are expected, as the losses are not caused directly by humans. However, as humans are the vectors that have been transferring and introducing these invasive species into ecosystems that would not normally have them, it is our responsibility to repair the damage humans have already done to native species’ populations.
To be sure, many human island populations rely on invasive species such as pigs and cats for their livelihood and health. So in order to reduce the effect of these creatures on the native species’ populations, community communication and participation is paramount. Finding alternative sources of income that are less harmful to the environment and instituting stricter policies in terms of cat care could both contribute positively to the conservation cause.
Island habitats are hot spots for biodiversity and serve as essential habitats for countless endemic species. Compiling data to perform predictive modeling is an essential way to put effective conservation programs into practice to protect these fragile ecosystems. However, the maintenance of these conservation programs is limited mainly by funding. And as conservationists are now able to more effectively determine programs that would make the biggest impacts on island populations, supporting this cause through legislative, community, and monetary backing is more important than ever.
- Erin E. McCreless, David D. Huff, Donald A. Croll, Bernie R. Tershy, Dena R. Spatz, Nick D. Holmes, Stuart H. M. Butchart, Chris Wilcox. Past and estimated future impact of invasive alien mammals on insular threatened vertebrate populations. Nature Communications, 2016; 7: 12488 DOI: 1038/NCOMMS12488
- University of California – Santa Cruz. (2016, August 18). Most island vertebrate extinctions could be averted, concludes new study: Control and eradication of invasive species could prevent as much as 75 percent of all island-level extinctions predicted for globally threatened vertebrates. ScienceDaily. Retrieved October 25, 2016 from http://www.sciencedaily.com/releases/2016/08/160818093315.htm