|Water birds on the Edge
The first circumpolar assessment of climate change impact on Arctic Breeding Water Birds
By Christoph Zöckler and Igor Lysenko, World Conservation Monitoring Centre, Cambridge, UK.
Summary by WWF
The World Conservation Monitoring Centre (WCMC) based in Cambridge, UK, is a joint venture between three partners in the World Conservation Strategy and its successor, “Caring for the Earth”: the IUCN, UNEP and WWF. The Centre provides information services on the conservation and sustainable use of species and ecosystems and supports others in the development of their own information systems.
Christoph Zöckler, a German biologist, is the WCMC’s biodiversity advisor. He has a specific focus on Arctic matters and migratory species. He runs the WCMC Climate Change and Biodiversity programme. Since 1995 he has joined five international expeditions in the Russian Federation, and four into the Russian Arctic.
Igor Lysenko, a Russian biologist, rejoined WCMC in 1997 after a period back in Russia. He co-ordinates WCMC’s activities on the Arctic and Russia and the development of analytic approaches to the integration of ecological data. Igor has extensive field research in the former USSR, and qualified at the Moscow State University. He worked previously with the Russian Ministry of Environment and the related Russian Institution for Nature Conservation.
This study was funded by WWF-UK.
Arctic warming faster than elsewhere.
Over the past century, global average temperature has increased by 0.5oC (0.9°F). There is international scientific consensus that this rise in temperature is “human-enhanced”. Nowhere has the warming been more pronounced than in the Arctic region, with temperature increases of up to 1.5ºC (2.7°F) per decade since the 1960s. As a result, the Arctic sea ice has lost 40 per cent of its volume in less than three decades.
While climate models predict a sharp increase in global average temperature ranging from 1.3 to 2.4oC (ca. 2.3 - 4.3°F) in the next 70-100 years and a doubling of carbon dioxide in the atmosphere, the Arctic region will experience the strongest warming: up to 5oC (9°F), with the most notable warming in winter and spring. There are regional differences predicted, with the greatest warming over the land areas of the Mackenzie and NW Canada, Alaska and Central Northern Russia. However, one region, from East Canada through South Greenland to Iceland, will actually experience a cooling throughout all seasons.
Among the most severely affected under a warming climate will be Arctic habitats, such as the tundra, which is expected to be among the first biomes globally to show direct impacts.
The importance of the Arctic for water birds
The Arctic is of major importance for many water birds. More than two thirds of all geese (an estimated 8.4 - 10 million) and almost 95 per cent of all Calidrid waders (about 14.5 million) breed in the Arctic. Although the water birds spend most of their annual life cycle outside the Arctic region, the three to four months they spend in these regions each year are critically important. Here they breed and rear their young. Geese and ducks also molt in the Arctic and are therefore very sensitive to climatic changes.
Models suggest that as the climate warms, forest cover is likely to spread northwards and replace areas of tundra vegetation. The structure and size of the Arctic tundra, the breeding habitat for millions of birds, is thus likely to be altered.
The purpose of the study was to investigate the potential impacts of climate change on a number of water birds species breeding in the Arctic.
This study can be broken into two parts:
The effect of climate and temperature on Arctic water birds
The study used the Hadley Centre’s climate model HadCM2 general circulation model (GCM) to assess the direct projected impacts of a change in temperatures and climate on the breeding conditions of five selected Arctic water bird populations.
The effect of climate-induced vegetation changes on Arctic water birds
The study looked at how the current distribution of a selected 25 species of Arctic breeding water birds might be affected by projected changes in Arctic vegetation under two different climate scenarios. The first was the Hadley Centre’s moderate scenario (HadCM2GSul) based on a rise in temperature of only 1.7°C (ca. 3.1°F) and an extreme scenario modelled by the UK Meteorological Office (UKLO) which predicts a rise of 5°C (9°F)1.
The timeframe used is where the concentration of CO2 in the atmosphere doubles, between 2070 and 2099. However, species will be affected much earlier than this as the climate gradually changes over the next decades.
The study is the first time that a circumpolar assessment of Arctic breeding water birds has been undertaken using GIS techniques to compute the large amount of data involved. It only looks at two of the many factors which affect the breeding and survival of Arctic water birds. While more information is certainly needed to complete the picture, these initial results show that urgent attention must be paid to this issue.
1. Changes in temperature may effect the White Fronted Goose
A gentle warming with earlier snowmelt and increasing temperatures in the Arctic summer would favour reproductive success for most bird populations. However, the shrinking of the birds’ habitat, the tundra, due to climate change could mean that an increase in population over one season may in turn result in increased pressure on the birds’ habitat.
In the case of the White-fronted Goose and the Taimyr population of the Knot, there is a significant correlation between a change in the mean June temperature and the number of juvenile birds hatched in the Arctic. With a rise in temperature, the number of juveniles hatched also rises. Two other birds studied, the Nearctic population of the Knot and the Curlew Sandpiper show no clear pattern to any particular to temperature.
Under the Hadley Centre model used in the study, the Taimyr-breeding White-Fronted Goose is unlikely to be particularly affected. However, the same model predicts a considerable cooling in West Greenland, the breeding grounds for a large population of the White-Fronted Goose, which is likely to drop in response. Most of these bird winter over in the UK, spending the winter in Scotland and NW Ireland.
2. Disappearing habitat as Arctic tundra shrinks: red list birds at risk
In its Second Assessment Report (SAR) in 1998, the UN Intergovernmental Panel on Climate Change (IPCC) predicted a major change of vegetation types in the Arctic, including a stated decrease of 40 to 57 per cent of the area currently covered by tundra vegetation, as it gets replaced by forest moving northward. As tundra is the most relevant habitat for Arctic water birds, there are major implications for bird population size and development. In particular, geese and Calidrid waders will be heavily affected as they breed almost entirely in tundra areas.
Although a change of the breeding habitat into unsuitable vegetation type is only one factor of many influencing the population, a first simple assessment indicates the magnitude of possible change. This suggests that a loss of 40 to 57 per cent of tundra would mean the loss of habitat for 4 to 5 million geese and about 7.5 million Calidrid waders by the period 2070 to 2099. Of course, the patterns of tundra loss will not be even, while the patterns of bird distribution within these habitat areas varies between species. Two of the three globally threatened species among the studied Arctic water birds will be strongly affected.
The Red-breasted Goose, although recovered in recent years, is still a threatened and vulnerable species as it is restricted to only a small geographical range. The Hadley model shows that it would lose 65 per cent of its current breeding range as it changes from tundra to forest. The UKLO model shows it would lose 99 per cent of its habitat. The population might decrease by two thirds or more. If the species is unable to shift northwards into the remaining tundra or adapt to shrub tundra habitats this could place the Red-breasted Goose closer to extinction.
The Spoon-billed Sandpiper is already one of the rarest and most threatened water birds in the Arctic breeding only in the Russian Far East with a population estimate of only 2,000 to 2,800 individuals. This study predicts that this bird would lose 56 per cent of its current habitat area.
Similarly restricted in its range is the Emperor Goose, which mainly breeds in the coastal marsh tundra in Beringia. Changes in the habitat structure will affect this rare goose considerably. In addition to the replacement of tundra by shrub or tree dominated habitats, the coastal wetlands in this area may be threatened by sea level rise. However, nobody has yet undertaken a detailed analyses of sea level rise in the Arctic. The Emporer Goose‘s status is already under consideration for listing into the Red Data Book of the globally threatened species. This additional threat from climate change would justify its inclusion.
Other species at risk
The Tundra Bean Goose is likely to be highly affected with a 76 per cent loss (93 per cent, according to the UKLO model) of its tundra habitat. The Greater White-fronted Goose, as well as most of the typical tundra breeding sandpipers, the Dunlin, the Red-necked Stint and the Curlew Sandpiper may all lose almost half of their potential breeding range. Taking into account more detailed information available on areas on high breeding density, for the Curlew Sandpiper the situation is ameliorated. Dunlin and Red-breasted Goose are affected in their current core areas.
Can they adapt?
It has been argued that geese in particular can adapt to changing surroundings. However, given that the area of tundra is likely to shrink considerably, this may limit this adaptability as the species fight for space.
Most waders will not be able to adapt to bushy or tree-like habitats and cannot expand into other habitats, except for a few areas gained by retreating glaciers. They will thus be forced to develop new strategies in the remaining tundra habitats for survival.
Those species not directly affected by the changing habitat are pushed further to the edge and, in particular those breeding in the far north, do not have any choice other than to compete with the northwards shifting individuals of the same and of other species.
Some birds like the Temminck Stint and the Long-billed Dowitcher are most likely to adapt, as been recently observed in semi-natural pastures along the northern edge of the boreal zone in Siberia. These species might possibly benefit from the change in vegetation.
Mitigation: a permanent downward trend in carbon dioxide (CO2) emissions of industrialised countries, leading to substantial reductions by 2010.
While we are already seeing signs of climate change appearing in the Arctic, it is not too late to stop the worst case scenario happening. This study once more underlines the urgent need to reduce the emissions of global warming gases to slow the rate of climate change.
The UK Government has announced measures to reduce its carbon dioxide emissions by 20 per cent by 2010. But there is no cause for complacency. Policies in several areas including renewables, energy efficiency and transport need to be strengthened to achieve the 20 per cent cut. Meanwhile, emissions are still rising fast on a global scale even though scientists have stated that we need to cut CO2 emissions by 60-80 per cent in the long-term. WWF calls on the UK Government to lead the world through political and diplomatic pressure.
In order to facilate adaptation to a changed climate, we need to seriously consider changes in habitat management. In the Arctic, grazing animals such as reindeer might keep the encroaching forest at bay and help preserve some of the tundra habitat.
Closer to home, sea level rise threatens many sites, such as in East Anglia, a wintering over site for the Knot and the Brent Goose. Depending on the model considered, sea levels could rise here between 13 and 74 cms (5 to 29 inches) by the 2050s. WWF advocates managed retreat as an option for some sites.
Need for further research
This study highlights the need for further research on water bird populations in West Greenland and North East Canada where cooling rather than warming is predicted, which could lead to a drop in breeding success in these birds.
Particular attention needs to be focussed on those species already threatened globally, namely the Tundra Bean Goose, the Red-Breasted Goose, the Spoon-billed Sandpiper and the Emperor goose. However, we also need to monitor the development of all other populations in respect to a changing climate.
One other area which needs attention is the impact of sea level rise in the Arctic itself.
Table 4: Possible scenario of changes to tundra habitat areas as predicted due to CO2 doubling, applying the HadCM2SUL model for 25 Arctic breeding water birds (areas in million sq km), ranked by the degree of impact. (Sources for distribution and population size see Rose & Scott 1997, Wiersma 1996, Zöckler 1998)