Ellen Cieraad's Research

Quantative plant ecology & physiology


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Double whammy caused by climate change

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.

(c) wikipedia

(c) wikipedia

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.


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A move across the world

Wordcloud_MinFreq12_Sept2015 Wordcloud_MinFreq25_Sept2015

After 14 years in New Zealand, we are now in the Netherlands and I am about to start my lecturer position at Leiden University. I recently created a word cloud* of abstracts of my published papers to date. The results (above) nicely depict my work at Landcare Research. While I look forward to keeping ties with some of my research and fabulous colleagues in New Zealand and elsewhere, I can’t wait to see what my new position at the Institute of Environmental Sciences (CML Leiden University) will bring!

* Word clouds are great ways to visually analyse text. Words that feature in your text more often are given greater prominence in the ‘cloud’. The number of words that make up your cloud depends on the threshold you place (effectively a minimum number of times that a word has to appear in the text). You can create these word clouds this really easy in some web applications (like worldle.net), but it’s also easy to do in R, and a lot more customisable.