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Migratory species threatened by global warming

Migratory species threatened by global warming

Migratory species threatened by global warming
November 19, 2006

Urgent action is need to prevent extinction of migratory species due to global warming says a new report from the United Nations Environment Programme (UNEP).

Citingt a number of examples, the report says that climate change is having an increasing impact on migratory species by dimishing habitat, forcing changes in migration routes, disrpting food sources, affecting nesting and breeding habits, and increasing susceptiblity to disease.

“Migratory species are in many ways more vulnerable as they use multiple habitats and sites and a wide suite of resources throughout their migratory cycle. So we need to bolster rather than clear habitats, reduce pollution to the land, freshwater and the marine environment, more sustainably manage water supplies for people and wildlife and enact other measures to assist animals and plants to cope and to adapt in a climatically changed world,” said Achim Steiner, UN Under-Secretary General and UNEP Executive Director. “Unchecked, climate change will pile on more pressure making it increasingly difficult for the world to… reduce the rate of loss of biodiversity by 2010.”

The report says that preventing climate change is also an economic priority.

The report says that global warming is linked to higher rates of cancer in sea turtles

“Take the host of the climate convention talks, Kenya. Its national parks and biodiversity generated $700 million in foreign exchange from tourism last year. If its parks and its biodiversity—from elephants to lions and rhino to wildebeest—were lost as a result of climate change, the impacts will be felt by the economy and the livelihoods of local people who depend on visitor income,” said Mr Steiner.

The report calls for significant reduction of greenhouse gas emissions combined with aggressive conversation measures that will help biodiversity adjust to changing climate conditions.

“Measures, such as maintaining a coherent network of stop over sites like wetlands; creating and expanding suitable habitat like field margins, hedgerows and ponds and developing and sustaining trans-boundary corridors that allow species to migrate as the climate changes, will be key to ensuring a healthy level of biodiversity now and in the future, ” said German Environment Minister Sigmar Gabriel.

Highlights from Migratory Species and Climate Change: Impacts of a Changing Environment on Wild Animals (Courtesy of the Conmvention on Migratory Species:

Changes in Migration Routes and Barriers to Migration

Changes in the length, timing and location of migration routes are being documented. In extreme cases, species have abandoned migration altogether. In other cases, species now migrate to areas where they have not been recorded other than as occasional vagrants.

• Exotic southern fish species like the Red Mullet, Anchovy, Sardine and Poor Cod are now being found in the North Sea. Fish species are ectotherimic (unable to regulate their body temperature) and their distribution and abundance are temperature dependent.

• European Bee-Eaters (Merops apiaster) once very rare in Germany are now breeding regularly across the country.

• The Rosy-Breasted Trumpeter Finch (Rhodopechys githaginea) is one of many birds once normally confined to arid North Africa and the Middle East now found in increasingly large numbers in southern Spain.

• The arrival of hundreds of Bewick Swans (Cygnus columbianus) flying in distinctive “V” formations used to herald the arrival of the British winter; ornithologists now report numbers down to double figures. Warmer weather on the continent and the absence of the NE winds which aid their migration are the likely reasons for the swans’ non-appearance in their traditional British wintering sites.

• Changing wind patterns are making it more difficult for passerine birds to make their migration in the Caribbean where spring storms are becoming more numerous and of greater intensity.

• This autumn several large Monarch Butterflies(Danaus plexippus), which migrate in millions every year from the USA and Canada to Mexico, have been blown across the Atlantic to England 5000 km away.

• Desertification increasing the size of the Sahara Desert will adversely affect the ability of Afro-European migrants to cross this ecological barrier successfully

Habitat Changes

The following changes are being witnessed:

• the permafrost is thawing and Arctic tundra is being replaced by forest;

• desertification is occurring in Africa;

• sea levels are rising;

• hurricanes are more frequent in the Caribbean;

• Antarctic waters are getting warmer and the ice is melting affecting sea salinity

Spatial distributions are changing — one study showed the range of certain taxa has moved on average by 6.1 km towards the poles and 1m in elevation in the space of a decade. Arctic-alpine specialists will face greater competition for habitat from other species which did not previously occur at higher altitudes and latitudes.

Alien species like the Pacific Oyster (Crassostrea gigas) brought to Europe for commercial reasons used not to be able to survive outside artificial pens. As the North Sea has grown warmer, the Pacific oyster has been able to breed in the wild and is now displacing native oysters in the Wadden Sea.

Incidence of flooding and resultant sediment run-off in Queensland, Australia damaged seagrass pasture leading to reduced growth and breeding rates for Green turtles (Chelonia mydas)

Baffin Bay hosts the largest concentrations of wintering Narwhals (Monodon monocerus). Here the trend has been for increased ice coverage in winter. The Narwhals depend on cracks in the ice to breathe and there have been several occasions when they have become trapped in the ice. Their site fidelity and the decrease in open water make them susceptible to Climate Change.

There is likely to be a general shift of species towards the poles, reducing the range of species most adapted to colder waters. The Common Dolphin (Delphinus delphis), a warm water species is increasing its range, while the White-beaked Dolphin’s (Lagenorhynchus albirostris) range is reducing. Predators are following their prey as prey species (eg fish) change their mean latitude and/or depth.


As migratory species are affected by climate change, then so are their prey species. For example, reproductive success of the non-migratory Great Tit (Parus major) and migratory Pied Flycatcher (Ficedula hypoleuca) is being affected by the changing availability of caterpillar food supplies. The temporal mismatch of prey and predator is part of a phenomenon known as “phenological disjunction”.

Reduced oceanic salinity causes shifts in the distribution of biomass constituents of the food chain with a tendency for poleward shifts in species assemblages and the potential loss of some polar specialist species like the Narwhal (Monodon monoceros).

It is doubtful whether Polar Bears (Ursus maritimus) will be able to adapt fast enough to changing ice conditions affecting the habitat of their seal prey species, and the disappearance of the ice threatens the bears’ survival.

Predator demographics are affected by prey. Market Squid (Loloigo opalescens) left southern California followed by the Short-Finned Pilot Whales (Globicephala macrorhynchus) which prey upon them. When the squid returned Risso’s Dolphins (Grampus griseus) filled the gap left by the whales; Bottle-nosed Dolphin (Tursiops truncatus) numbers rose at the same time but did not decline again after the end of the El Niño event.

Krill may be outcompeted by other species more tolerant of warmer water with repercussions for species higher up the food chain, including penguins, albatrosses, seals and cetaceans, despite their wide foraging ranges.

Animals and plants specialised to live in Arctic and Alpine environments will also face greater competition for food from other species which did not previously inhabit higher altitudes.

Data gleaned from strandings show that changes in Sperm Whale (Physeter macrocephalus) distribution in the NE Atlantic can be attributed to shifts in the North Atlantic Oscillation and to the knock-on effects on the squid species upon which they prey.

Abundance and quality of prey species is important, especially in stopover sites, and most particularly in stop-over sites adjacent to large barriers such as the Sahara Desert.

Severe breeding failures affected important seabird colonies in Scotland as a result of warmer waters leading to a loss of plankton and reduced fish numbers. In some cases 100% breeding failure occurred in some years. Following the Sahel drought of 1968-69 Whitethroat Warbler (Sylvia communis) numbers are still only 25% of what they once were.

Breeding/Nesting/Reproduction Success

Reduced breeding success (probably prey related) is apparent in some Antarctic species. In birds, abnormally heavy rainfall can adversely affect mortality rates among fledglings.

The El Niño Southern Oscillation in 1982 is thought to have resulted in the loss of an entire year of Galapagos Fur Seal (Arctocephalus galapagoensis) pups and abnormally high mortality rates among juvenile seabirds.

The El Niño Southern Oscillation will also have impacts on Green turtle (Chelonia mydas) breeding migrations, and rising sea levels may lead to the loss of turtles’ egg-laying beaches.

Cues in the wintering grounds that it is time to migrate may no longer be a good measure of conditions in the breeding grounds (another example of the phenomenon of “phenological disjunction”).

Bats have been known to arouse from hibernation early affecting the females’ reproductive cycle.


Reduction of sea ice will impact on Ringed Seal (Pusa hispida), Bearded Seal (Erignathus barbatus) and Walrus (Odobenus rosmarus) populations that use ice floes for resting, moulting and giving birth.

As mentioned above, the Lesser White-fronted Goose (Anser erythropus) is a particularly vulnerable species being reliant on a small number of discrete stopover sites.

Incidence of Disease

Fibromapilloma tumours in Green turtles (Chelonia mydas) are thought to grow faster in warmer waters and their prevalence has increased since the 1980s. Other diseases and parasites thrive in higher temperatures and will impact more profoundly on the populations of their victim/host species.

Global warming may engender algal blooms and contribute to epizootics. Mass die-offs of marine mammals have increased, and where the cause has been viral, environmental factors have contributed to the outbreaks or reduced the ability of the animals to fend off the illnesses.

Reduced food supplies for Cetaceans in warmer waters affect the condition of females and interfere with the frequency of their reproductive cycles.

Reduced rainfall in the eastern Mediterranean caused a drop in nutritional levels in the sea affecting the health and condition of Striped Dolphins(Stenella coerulealba).

Feminisation of Populations

The sex ratio of turtle hatchlings is temperature dependent in both the Dermochelyidae and Chelonidae families. Higher temperatures in the range 25-32OC lead to greater number of female young (and lower temperatures to more males).

An imbalance of 1 male:2 females or 1:3 has no ill-effect but if the proportions move towards 1:4, populations may be adversely affected. Some nesting beaches are seeing temperatures rise above 34 OC which is often lethal.

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This article uses quotes from a WWF news release.

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