A new paper in Nature Communications by Regan Early (University of Exeter, Cornwall) et al. projected global patterns of threats of invasive species based on 21st century patterns in trade and traffic and environmental change. The authors found that “1/6th of the global land surface is vulnerable to invasions, including substantial areas in developing economies and biodiversity hotspots.” They also mapped countries’ capacities to prevent and manage invasions. They found an increase in invasion risk in many countries with historically low levels of invasions (in the Southern hemisphere) – several of these countries are at particularly high risk due to a limited capacity to deal with invasive species.
Revenge of the goldfish! Dumped pets growing into giant monsters! This article in treehugger left me wondering about the fate of my first goldfish, won from the Milton Fall fair, released into my hometown pond unknowingly by a naïve animal-lover who felt guilty for keeping him in a confined space. The pet trade is a major pathway by which species are introduced, establish, and sometimes become invasive. With limited regulations, one of the best ways to mitigate future invasions via this pathway is to educate the public (i.e., young animal lover kids with seemingly good intentions). Goldfish are a widespread invasive in several countries, becoming very large outside of the confines of their tanks, eating eggs of native species, introducing disease, and disturbing habitats. The original study is by Stephen Beatty et al. in Ecology of Freshwater Fish.
A longstanding controversy in invasion biology is that there is limited evidence that invasion cause species extinctions via competition, especially in plants. In fact, several studies show that non-native species actually increase diversity. These are valid points with implications for management – the impacts of invasions are overstated and in many cases, we should just let them be. While I am certainly not an advocate for killing all invasive or non-native species, I find these arguments problematic for several reasons. A recent article in Scientific American highlights one reason, that invasive species could push some species along an extinction trajectory. While there are few documented cases of invasions causing extinctions, “plant extinctions are an agonisingly slow process,” stated one of the authors Dave Richardson (Centre for Invasion Biology at Stellenbosch University) of the original study in AOB plants. Population extinctions precede species extinctions and plant population loss, fragmentation of populations, and shrinking populations all increase risks of extinction. Thus, just because we don’t have direct evidence that invasions cause extinctions shouldn’t preclude us from trying to manage invasions that contribute to the movement of species towards extinction.
We know that only a small sample of non-native species that establish outside of their historical range become invasive (spread and impact). Capybaras (large rodents) are likely becoming established in Florida from a handful of individuals that escaped from a research facility. Although not invasive yet, they have the potential to become invasive because they are social and resilient animals that eat crops. As species establish (start to grow in population size) and become invasive, they are increasingly difficult and expensive to manage. Thus, it is important to try to manage small populations of species before the form larger populations and spread. The challenge is then trying to predict if species will become invasive and if management is warranted.
This is very nice read on the success story of the sequential eradications (complete removal of a population of an invader) of several invasive species from Santa Cruz Island in California. Management of invasive mammals on islands has been a huge success. There are hundreds of successful eradications, and in most cases eradications lead to conservation gains. However, mammals are easier to eradicate than other invasive species such as hard to detect insects or plants with seed banks. The most recent eradication effort on Santa Cruz is perhaps the hardest of all – the Argentine ant. Eradication success decreases with the likelihood that species will reinvade and when finding every last reproductive individual (in this case queens) is difficult. The team thinks they have a good chance of killing most, but not all of the ants – all is a pretty tall order!
The future for lionfish might be shocking! There is bad news for invasive lionfish – the non-picky invasive predator that is ravaging fish and reef communities in the Atlantic. The bad news is the “Lionfish Terminator,” a robot that seeks out, sneaks up on, and zaps the fish. These fish are hard to manage because they swim deep, but not too deep for the robots. Advances in technology like this will greatly aid in more effective environmental management.