Invasive species can have detrimental effects on ecosystem services, including food security and indigenous biodiversity. Similarly, climate change has been predicted to affect global food provision and the stability of ecosystems. Many studies assess the direct effect of either of these issues facing today’s world; however, of course they operate in tandem and this can create complex effects. While it is well established that climate change may facilitate the abundance and/or range expansion of invasive species, it is less known that it may also impact the ability to control and manage this invasion. If, for example, climate change results in the increase in abundance of an invertebrate crop pest, and at the same time in a decrease of a natural pest control agent (for example, insectivorous birds), then climate change can accelerate the impacts of invasions, and create a ‘double whammy’ for the receiving ecosystem. Similarly climate change may alter the effectiveness of ways to control invasive species.
In a recent article, we show that increasing air temperatures over >60 years in New Zealand has reduced the window of opportunity to effectively control an invasive mammalian pest (European rabbit Oryctolagus cuniculus – using Central Otago, South Island, as an example).
Latham ADM, Latham MC, Cieraad E, Tompkins DM, Warburton B 2015. Climate change turns up the heat on vertebrate pest control. Biological Invasions 17(10): 2821-2829. doi: 10.1007/s10530-015-0931-2
Anthropogenic control of invasive vertebrate species is most effective in times when natural food is limiting. In the case of rabbits in temperate southern New Zealand, the most effective period of control is during the coldest period in winter, when temperatures are sustained below approximately 5°C and the above-ground palatable vegetation available to rabbits reaches an annual low. Our study found that the milder winters in recent years resulted in the window of control starting later and ending earlier in the year, and that those windows are increasingly punctuated by warm temperatures. Overall this has resulted in suboptimal conditions for poisoning because of the higher availability of natural foods.
While longitudinal records detailing the effectiveness of control operations are not available, this study suggests that the trend towards warmer winters over the past >60 years has significantly reduced the window of time for effective control of rabbits in temperate New Zealand. As winters are likely to continue to warm, alternative methods of management warrant investigation.
Climate change may thus exacerbate the unwanted impacts of invasive species by reducing our ability to manage them effectively.