Aliens in a warming world

Andrea Smith.

Dealing with the direct effects of climate change, like rising sea levels and more extreme weather events, is daunting enough. But there are also indirect effects of climate change we should be worried about. One of these is the spread of invasive alien species into new areas as a result of warming temperatures.
Alien species are plants, animals and micro-organisms that are introduced beyond their native range by humans, either intentionally or accidentally. Most never become a problem, but a small proportion end up getting out of control, and can cause widespread damage, not only to native ecosystems and biodiversity, but also to the economy and human society.
Take for example the zebra mussel, introduced by accident to Lake St. Clair from Europe in ship ballast water during the late 1980s. In just over two decades, this lowly invertebrate has spread throughout the Great Lakes and to many inland lakes and rivers in Ontario, Quebec and the northern states.
In the process, the zebra mussel has led to declines in populations of native mussels, plants and fish. It has also caused extensive problems for industry, clogging pipes at utility plants, factories and water treatment facilities. The mussel has had negative impacts on recreational water use as well, by encrusting boat hulls, piers and moorings, and polluting swimming areas. Over the next 10 years, the U. S. Fish and Wildlife Service predicts that this invasive species will result in billions of dollars of damage in the Great Lakes alone.
On a global level, invasive alien species are a major environmental and socio-economic problem. Rising trade and travel in recent decades has provided countless opportunities for alien species to be introduced and become invasive in new parts of the world. Invasive species are now considered the second greatest threat to biodiversity (after habitat loss) and are estimated to cost more than $1.4 trillion in damage and control annually worldwide (roughly five per cent of the global economy).
Climate change offers even more opportunities for alien species to spread, as areas that were previously too cold for many species to survive warm up. The International Panel on Climate Change warns that this will lead to drastic changes in the distribution of many species, and overwhelming negative consequences for global biodiversity, as well as ecosystem goods and services. In Canada, this will mean new invasive species expanding their ranges from southern origins (such as the States), as well as existing invasive species (like the zebra mussel) spreading further across the country.
My recent work has focused on reviewing how invasive species might spread in Canada under climate change, and what the anticipated impacts will be. What we know relates mainly to invaders that already occur in Canada, either as native species that have spread beyond their range (like ticks that cause lyme disease, mountain pine beetles, and smallmouth bass) or as established invaders (like the gypsy moth).
All of these species are expected to expand northward in coming years, resulting in widespread damage to forest and freshwater biodiversity, carbon sequestration, and public health.
For example, lyme disease is forecast to spread 1,000 kilometres north in eastern Canada over the next 70 years, becoming a major public health challenge. The spread of smallmouth bass, meanwhile, will likely lead to the disappearance of native carp and trout in many Ontario lakes.
Here in Muskoka, we are already familiar with several invasive species, like the spiny waterflea (which is devastating native zooplankton communities in our lakes) and giant hogweed (which has sap that causes severe burns and blindness). Climate change means that many new invaders may be on our doorstep soon.
Given the seriousness of the problem, you might think plans and strategies were in place, or in development, to tackle the emerging threat of invasive species under climate change. But, in Canada, at least, policy is missing at both the federal and provincial levels on this issue.
Time is running out. We need strong leadership now that acknowledges the significant link between climate change and invasive species. We need action that focuses both on climate change mitigation and on halting the spread of invasive species in a warming world. On the climate change front, this could include a clear and co-ordinated national plan to lower greenhouse gas emissions in a meaningful way. On the invasive front, this could include more research to forecast what invaders are anticipated and where, increased monitoring to prevent new invaders getting in, and increased efforts to restore and protect native ecosystems so they are resilient to invasion.
Andrea Smith is a local biologist who works on invasive species issues through the Canadian Aquatic Invasive Species Network, York University, and the Ontario Ministry of Natural Resources.

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