Mass migration of species to cooler climes has profound implications for society, pushing disease-carrying insects, crop pests and crucial pollinators into new areas, says international team of scientists
Damian Carrington The Guardian 30 Mar 17;
Global warming is reshuffling the ranges of animals and plants around the world with profound consequences for humanity, according to a major new analysis.
Rising temperatures on land and sea are increasingly forcing species to migrate to cooler climes, pushing disease-carrying insects into new areas, moving the pests that attack crops and shifting the pollinators that fertilise many of them, an international team of scientists has said.
They warn that some movements will damage important industries, such as forestry and tourism, and that tensions are emerging between nations over shifting natural resources, such as fish stocks. The mass migration of species now underway around the planet can also amplify climate change as, for example, darker vegetation grows to replace sun-reflecting snow fields in the Arctic.
“Human survival, for urban and rural communities, depends on other life on Earth,” the experts write in their analysis published in the journal Science. “Climate change is impelling a universal redistribution of life on Earth.”
This mass movement of species is the biggest for about 25,000 years, the peak of the last ice age, say the scientists, who represent more than 40 institutions around the world. “The shifts will leave ‘winners’ and ‘losers’ in their wake, radically reshaping the pattern of human wellbeing … and potentially leading to substantial conflict,” the team warn. “Human society has yet to appreciate the implications of unprecedented species redistribution for life on Earth, including for human lives.”
Climate change driven by human greenhouse gas emissions is not just increasing temperatures, but also raising sea levels, the acidity of the oceans and making extreme weather such as droughts and floods more frequent. All of these are forcing many species to migrate to survive.
“Land-based species are moving polewards by an average of 17km per decade, and marine species by 72km per decade” said Prof Gretta Pecl at the University of Tasmania in Australia, who led the new analysis.
There are many documented examples of individual species migrating in response to global warming and some examples of extinctions. But Pecl said: “Our study demonstrates how these changes are affecting ecosystems, human health and culture in the process.”
The most direct impact on humans is the movement of insects that carry diseases, such as the mosquitoes that transmit malaria shifting to new areas as they warm and where people may have little immunity. Another example is the northward spread in Europe and North America of the animal ticks that spread Lyme disease: the UK has seen a tenfold rise in cases since 2001 as winters become milder.
Food production is also being affected as crops have to be moved to cooler areas to survive, such as coffee, which will need to be grown at higher, cooler altitudes, causing deep disruption to a global industry. The pests of crops will also move, as will their natural predators, such as insects, birds, frogs and mammals.
Other resources are being affected, with a third of the land used for forestry in Europe set to become unuseable for valuable timber trees in the coming decades. Important fish stocks are migrating towards the poles in search of cooler waters, with the mackerel caught in Iceland jumping from 1,700 tonnes in 2006 to 120,000 tonnes in 2010, prompting a “mackerel war” with neighbours in whose waters the fish had previously been.
The benefits to humans being provided by species, and the complex ecosystems they live in, are also at risk. Mangroves, for example, are migrating polewards in Australia and in the southern US, meaning the storm protection and fish nurseries provided are being lost in some places.
The shifting of animals and plants into new areas can sometimes lead to drastic changes, as those areas have not evolved with the incomers and lack natural defences. In Australia’s seas, kelp forests are being destroyed by an influx of tropical fish that eat them, threatening the important rock lobster trade.
The scientists also warn of feedback effects that can exacerbate climate change, citing the poleward spread of bark beetles in northern hemisphere forests. The beetles attack trees that may already be weakened by warmer, drier conditions, leading to more severe pest outbreaks and tree deaths. This in turn provides more fuel for forest fires, releasing more planet-warming carbon dioxide.
“Climate-driven species redistributions shouldn’t only be a concern for conservation biologists – they should worry everyone,” said Nathalie Pettorelli, at the ZSL Institute of Zoology in the UK, and one of the analysis team. “The world as a whole isn’t adequately prepared to handle the range of issues emerging from species moving across local, national, and international boundaries.”
She said plans to cope with climate change urgently needed to take these issues into account and said everyone could play a part in collecting much needed data on shifting species. “Citizen science can really help,” she said, with people reporting when they see new species in a region and some schemes are already set up.
