Where do you go when you’ve reached the top of a mountain and you can’t go back down?
It’s a question increasingly relevant to plants and animals, as their habitats slowly shift to higher elevations, driven by rising temperatures worldwide. The answer, unfortunately, is you can’t go anywhere. Habitats shrink to the vanishing point, and species go extinct.
That scenario is likely to be played out repeatedly and at an accelerating rate as the world continues to warm, Stanford researchers say.
By 2100, climate change could cause up to 30 percent of land-bird species to go extinct worldwide, if the worst-case scenario comes to pass. Land birds constitute the vast majority of all bird species.
”Of the land-bird species predicted to go extinct, 79 percent of them are not currently considered threatened with extinction, but many will be if we cannot stop climate change,” said Cagan Sekercioglu, a senior research scientist at Stanford and the lead author of a paper detailing the research, which is scheduled to be published online this week in Conservation Biology.
The study is one of the first analyses of extinction rates to incorporate the most recent climate change scenarios set forth earlier this year in the reports of the Intergovernmental Panel on Climate Change (IPCC), which shared the Nobel Peace Price with Al Gore.
The researchers modeled changes to the elevational limits of the ranges of more than 8,400 species of land birds using 60 scenarios. The scenarios consisted of various combinations of surface warming projections from the 2007 IPCC report, habitat loss estimates from the 2005 Millennium Ecosystem Assessment (an evaluation of the planet’s ecosystems by 1,360 experts around the world), and several possibilities of shifts in elevational range limits.
The worst-case scenario of 6.4 degrees Celsius surface warming combined with extensive habitat loss produced the estimate of 30 percent of land bird species going extinct by 2100. Increasing habitat loss exacerbates the effects of climate change because organisms seeking more suitable conditions will be less likely to find intact habitats. Even with an intermediate 2.8 C warming, 400 to 550 land-bird extinctions are expected.
”Vegetational shift is the key issue here,” Sekercioglu said. ”Birds will follow the shift in habitat.”
All plants have certain temperature and precipitation requirements they need to flourish. As lowlands become too warm for some species, higher slopes that were formerly too cool become better suited to their needs, and the distributions of plants slowly move upward. That shifting of populations renders bird species vulnerable to a host of complications.
Topography itself is a major issue. Each bird species is only found between specific elevations, limits based mainly on the temperatures at which it can survive and the presence of the plants, insects and other animals on which it feeds. Temperature decreases as one goes up a mountain, so as the lowlands become warmer, plant and animal communities need to move higher in order to remain in their required microclimates. Most bird species live in the tropics, mostly in lowland environments. In many of these areas, there may be no significantly higher slopes to which they can retreat. But even the presence of hills or mountains does not guarantee the survival of a species.
As one moves upslope, the extent of the area encompassed by a given elevational range almost always decreases. It’s a matter of simple geometry. The circumference of a mountain is typically smaller near the summit than at its base, so a range of, say, a hundred vertical meters occupies a far smaller band of area near the top than it does down at the base.
And once the summit of a mountain becomes too hot for a species or its preferred vegetation type, the habitable area is reduced to nothing.
”It’s like an escalator to extinction. As a species is forced upwards and its elevational range narrows, the species moves closer to extinction,” Sekercioglu said.
In some instances, species can expand their ranges, which the authors also considered in their models. If warming is limited and a species adapts, only the upper limit of a species’ elevational range might rise. As warming continues, however, the lower bound is likely to rise, as well.
Additional threats include interactions between the rising temperatures and other environmental factors. For example, as Hawaiian mountains get warmer, mosquitoes carrying avian malaria, to which most native bird species have no immunity, are moving upslope, invading the last refuges of birds already on the brink of extinction. In Costa Rica, toucans normally confined to lower elevations are colonizing mountain forests, where they compete with resident species for food and nesting holes, and prey on the eggs and nestlings of other bird species.
In addition, plant species that currently share a habitat may not all react the same way to temperature and moisture changes. Some species may be forced upslope while others are able to linger behind, tearing apart plant and animal communities even if all the species survive. Differences in soil composition can further disrupt plant communities. If soils at higher elevations are inhospitable to some plant species, those species will be wedged between a fixed upper bound and a rising lower bound until they are squeezed out of existence.
Until now, highland species have been less threatened by habitat loss and hunting, simply because most people live in flat lowlands instead of the steeper highlands. Compared to lowland birds, however, highland species are not only more sensitive to temperature changes, but their populations also are more isolated from each other, as mountains effectively constitute habitat islands surrounded by a sea of hotter lowlands.
The study also has shown that sedentary birds, which comprise over 80 percent of all bird species, are much more likely to go extinct from climate change than are migratory birds. That suggests that many sedentary mountain species currently thought to be safe are actually jeopardized by global warming. All in all, climate change is likely to be especially hard on the hundreds of bird species endemic to tropical mountains.
But in part because of the remoteness of the mountains and in part due to a lack funding for ornithological studies in most tropical countries, there are few data on these birds’ responses to climate change. Crucial remote sensing data are also becoming less available, as government satellites like Landsat age and as image distribution moves increasingly to the relatively expensive private sector.
”To effectively monitor the rate of change as warming progresses, especially in the species-rich tropics, we need a lot more data on birds’ distributions and on the speed and extent of birds’ elevational shifts in response to climate change,” Sekercioglu said.
Perhaps the most worrisome finding is that each additional degree of warming will have increasingly devastating effects. The authors estimate that an increase of 1 C from present temperatures will trigger roughly 100 bird extinctions. But if the global average temperature were to rise 5 C, from that point on an additional degree of warming, to 6 C, would be expected to cause 300 to 500 more bird extinctions.
”This emphasizes the importance of any measure that reduces surface warming, even if we cannot stop it altogether,” Sekercioglu said. ”Even a reduction of 1 degree can make a huge difference.”
”Giving up the fight against global warming would be the true disaster,” he added.
Communities Across the Globe Getting to Grips with Climate Change
UN Environment Programme/Global Environment Facility Report Points to Real Possibilities for Climate Proofing Economies, Livelihoods and Infrastructure
UN Climate Convention – 2 to 14 December – Bali and Beyond
Bali/Nairobi, 4 December 2007 – The way farmers in the Sudan, flood-prone communities in Argentina and dengue-challenged islands in the Caribbean are beginning to adapt to climate change are distilled in a new report launched today.
The five-year Assessments of Impacts and Adaptations to Climate Change provides new and inspiring examples of how vulnerable communities and countries may ‘climate proof’ economies in the years and decades to come.
In doing so, the assessments lay a foundation upon which at-risk nations and the international community can build and fund a credible and timely response to the climate change that is already underway.
Choices – the Tortoise and the ‘Hare’
The report underlines that factoring climate into development strategies is do-able but that in some cases hard choices may have to be made.
In a modern re-run of Aesop’s famous fable, it highlights the case of tortoise and the rabbit rather than hare.
One study in South Africa’s world famous Cape Floral Kingdom – a unique and economically important ecosystem – indicates that climate change is likely to increase the risk of extinction of the highly endangered riverine rabbit.
However, adaptation measures might conserve the padloper tortoise highlighting how across sectors – from biodiversity to agriculture, water and infrastructure – investments in adaptation will need to be intelligently and cost-effectively targeted.
The more than $ 9 million assessment has been funded by the Global Environment Facility (GEF), implemented by the UN Environment Programme (UNEP) and executed by the START secretariat in Washington DC and TWAS, the Academy of Science for the Developing World in Trieste, Italy.
Twenty-four case studies were carried out under the AIACC project, including eleven in Africa. They encompass food security in the Sahel; smallholder farmers and artisanal fishing communities in South America; coastal townships of small islands in the Pacific; pastoralists in Mongolia; rice farmers in the lower Mekong basin.
More than 350 scientists, experts and ‘stakeholders’ from 150 institutions in 50 developing countries and 12 developed ones took part. Pilot adaptation programmes have been drawn up in some cases and some of these have already been tested with many encouraging results.
The findings, stories and recommendations from the AIACC case studies are presented in two newly published books, Climate Change and Vulnerability and Climate Change and Adaptation. Results of the project are also summarized in the final technical report and detailed in a number of supporting reports available at http://www.start.org.
Community Involvement and Early Warning
A key success of the assessment has been the increased awareness among the scientists, governments and local communities as to the importance of adaptation.
It also highlights in many cases the need to develop early warning systems especially, but not exclusively in Africa, where weather and climate monitoring networks remain sparse, under funded or poorly maintained.
Achim Steiner, UN Under-Secretary General and UNEP Executive Director, said: “2007 has, as a result of the work of the Intergovernmental Panel on Climate Change (IPCC), been a year in which the science of climate change has reached a finality – it is happening, it is unequivocal”.
“2007 has also seen clear and cost effective strategies for cutting greenhouse gas emissions put on the table from improved energy efficiency in buildings to ones that address deforestation and agriculture,” he added.
“One of the big missing links has been adaptation, both in terms of adaptive strategies and in terms of resources for vulnerable communities. This assessment, involving experts across the developed and developing world, lays a solid and much needed foundation – a foundation upon which adaptation can become part of country development plans and built into international assistance including overseas development aid,” said Mr Steiner.
Monique Barbut, Chief Executive Officer and Chairperson of the GEF, said: “The GEF has a long history working with the world’s most vulnerable countries
that want environmentally-friendly ways to adapt to changing climate without sacrificing key development goals”.
“As this wide sweeping assessment shows first hand, we are moving forward in a very focused way to weave adaptation strategies into daily practice. GEF money is working today to ensure that food security, access to drinking and irrigation water, sound public health and other basic needs are protected now and into the future,” she added.
Neil Leary of the International START Secretariat in Washington, who along with the Academy of Sciences for the Developing World in Trieste, have executed the project said: “Adaptation to climate hazards is not new. People have always been at risk from the climate and have continually sought ways of adapting. Still, variations and extremes of climate regularly exceed abilities to cope, too often with devastating effect, and give evidence of what has been called an adaptation deficit”.
“Now climate change threatens to widen the deficit, as shown by the AIACC studies. But the AIACC studies also find and document a variety of adaptive practices in use that reduce vulnerability. Building on and improving many of these practices can serve as a good starting point for adapting to the growing risks from climate change. Reducing emissions of the gases that cause climate change is necessary. But adaptation is necessary too,” he added.
The decision to carry out the assessments was at the request of the Intergovernmental Panel on Climate Change (IPCC). Rajendra Pachauri, chair of the IPCC said the peer reviewed reports had made a significant contribution to the IPCC’s landmark fourth assessment report published this year.
Highlights – Africa
The Berg River dam was commissioned in 2004 to supply Cape Town, South Africa with water for uses such as drinking and irrigation. Climate change is likely to put increased stress on water availability over the coming decades in the Western Cape region.
The researchers looked at various costs and benefits linked with a variety of adaptation measures including increasing the capacity of the dam to creative water markets. They conclude that “substituting water markets for the existing allocation system substantially increased the simulated marginal cost of water to urban users and led to reduced consumption”.
The researchers add that such a system would have to take into account the impact on poor households in the Cape Town area.
Another study has looked at cost effective adaptation opportunities in parts of the Cape Floral Kingdom in the Western Cape – a biodiversity hotspot and major tourist attraction.
By 2050, climate change may result in loss of habitat for over 10 per cent of species and six per cent would need to move to new locations. Wildlife corridors will help.
One option might also be to expand the conservation network including reserves. Overall however a more cost effective option will be to pay farmers to manage land for conservation or to encourage more environment-friendly farming, the study concludes.
Some projections of climate change suggest steadily declining rainfall from 2010 to the end off the century in West Africa. Should a drier climate come to pass, millet, a key staple crop, would undergo a gradual decline in yields unless adaptation measures are taken.
The researchers looked at four responses including the introduction and extension of irrigation, the introduction of new crop varieties and the use of fertilizers.
The findings show that millet crop yields can be increased even in a climate constrained world with harvests improved by 13 per cent if new varieties are deployed; up to a third if fertilizers are made available and increased by 37 per cent if irrigation is introduced.
The analysis indicates that new varieties and expanded use of fertilizer can be cost effective measures for maintaining grain yields in a drier climate. However, the adoption of irrigation is found to be too costly to be economically viable for growing relatively low valued grains.
The actual income for poor farmers might fall without assistance as irrigation will require the purchase and maintenance of diesel-powered water pumping kit. Solar-powered pumping could reduce the costs by perhaps 60 per cent.
Here three case studies were undertaken in the dry, drought-prone and often degraded lands of Bara Province of North Kordofan; Arbaat, Red Sea State and El Fashir, North Darfur to see if communities can be made more resilient to climatic shocks.
The findings indicate that relatively minor but well thought out interventions, if supported by community involvement and involving in many cases the empowerment of women and services such as veterinary to micro-credit, can boost livelihoods and reduce vulnerability.
In Bara, a pilot to develop sustainable livelihoods has been tested under an UN Development Programme-GEF initiative called the Community-Based Rangeland Rehabilitation for Carbon Sequestration’.
Small-scale irrigated vegetable gardens, pest management, a switch from goats to sheep, sand dune stabilization and other measures have been tested as adaptive measures.
The project in Bara has seen land rehabilitation rise by close to 60 per cent; the carrying capacity for livestock rise by over 45 per cent and forage production climb by 48 per cent.
In Arbaat, various practical and institutional measures have been tested including the deployment of rainwater harvesting and tree planting alongside micro credit schemes, adult literacy for women and training for improved agricultural practices.
The work in Arbaat has led to land productivity increasing by 12 per cent and crop productivity by almost a fifth with improvements in both water quality and quantity.
In El Fashir, the community has developed their own response to a changing climate now supplemented by outside assistance.
Utilizing a water collection system known as trus alongside earth dams.
Responding to the encroachment of sand over fertile soils by adopting magun cultivation involving the sinking of regular placed holes five to 15 cm deep in which to plant melon and other seedlings.
Diversifying crop production including pumpkin, okra, tomatoes, citrus fruits, cucumbers, tobacco, millet and sesame.
The establishment of trades union – the Traditional Farmers and Fruits and Vegetable Unions – to organize production, harvesting and distribution.
The project has registered a 50 per cent improvement in productivity of the land as a result of dramatically increased water harvesting.
A study of livestock – a key mainstay of the Mongolian economy – indicates that climatic impacts are already affecting productivity.
Over the period 1980 to 2001, the average weight of sheep, goats and cattle have fallen by an average of 4kg, 2kg and 10 kg. Wool and cashmere production are also down.
Models forecast increasing impacts as a result of climbing air temperatures including a spread of the desert area to the north by 2080. The weight of ewes in the summer is expected to decline by 50 per cent by the same date as a result of factors including heat stress.
The area of land in Mongolia suitable for grazing may decline from 60 per cent now to 20 per in 2080.
There is also concern that climate change may intensify weather extremes from drought to a phenomenon called dzuds – sudden spurts of heavy and long-lasting snowfall that bar animals from access to grazing land.
In 1999-2000 a dzud event saw herders losing more than a quarter of their livestock forcing Mongolia to request international assistance.
A suite of adaptation measures are pinpointed ranging from insurance systems and risk funds to buffer herders against climatic shocks up to improved forecasting of extreme weather events.
The revival of traditional pasture management, reforestation of flood plains and irrigation of pasture lands are also proposed alongside the provision of animal shelters.
Studies on climatic impacts and possible adaptation strategies have also been carried out for Indonesia.
Here the Citarum watershed emerges as highly vulnerable to climate change with more extreme floods and droughts likely over the coming decades.
Studies indicate that many of these impacts can be minimized if forest cover is kept above 25 per cent. The authorities and the private sector are now looking at paying communities upstream to maintain rather than fell the forest – a system known as payment for ecosystem services.
“The electricity company Indonesian Power is also willing to support community reforestation activities through a community development programme. With these efforts, it is expected that a minimum forest cover of 25 per cent could be achieved to ensure a continuous supply of water during dry season and extreme drought years,” says the AIACC report.
A further study in Asia has focused on the Heihe River Basin in Northwestern China – an area where water supplies are already heavily utilized if not overtly utilized and where conflict of water is already occurring.
The study forecasts that that average temperature rises of between 2.5 degrees C and 6.5 degrees C could occur by 2050.
A vulnerability assessment has also been undertaken indicating a range of serious emerging risks as a result off climate change including very severe water shortages; increased floods and droughts and impacts on food supplies.
“Ecosystem vulnerability to climate change in the Heihe River Basin is also high. The degree of vulnerability is highest in the lower reach of the basin which is largely unmanaged grassland,” says the report. Indeed, it warns that increasing pressure from climate, population and over use of nature-based resources could trigger ecological collapse in some areas.
The researchers have drawn up a list of adaptation options that might assist the communities of the Heihe River Basin.
These include water-saving irrigation strategies; leak reduction from irrigation channels; conserving soil moisture by plastic films, straw and deep plowing methods up to the establishment of market mechanisms such as water permits and water allocation policies.
Argentina and Uruguay
One AIACC study here has focused on the likely impact of climate change on floods and storm surges on coastal and estuary lands on La Plata River.
Strong winds, high tides and the natural features of the La Plata mean flooding occurs already with vulnerable areas identified as Samborombon Bay and up stream as far as Buenos Aires and its surrounds.
The researchers modeled likely future floods as a result of climate change including effects on storm surges and sea level rise.
It is likely that the level of the La Plata will rise higher than average sea level rise because of changes in wind patterns with the increase higher on the Uruguay coast and greater up the river’s estuary.
The report estimates that, as a result of climate change and a modest one per cent per year increase in population, the population at risk of floods could be 1.7 million by 2070 – more than three times the current numbers at risk of floods.
Around a quarter of a million people will be at risk of flooding each year or six times the current number at risk.
Property and infrastructure losses for the period 2050-2100 could range from five to 15 billion US dollars. Part of the loss calculation is based on the assumption of a single storm surge surging into the Metropolitan region of Buenos Aires.
The findings have been presented to the governments concerned alongside recommendations that include a review of coastal and city defenses and of early warning systems and flood response strategies.
The report also flags up concern that a traditional adaptation strategy is being ignored with increasing numbers of poor settlements and ‘gated communities of upper middle class people’ being sited on very low coastal lands.
Dengue hemorrhagic fever and dengue shock syndrome are forecast to increase in the tropics and sub tropics as a result of climate change.
In the Caribbean cases have climbed from a few hundred a year in the 1980s to as many as 8,000 a year since the early 1990s.
There are concerns that rising cases of dengue could impact on the economically-important tourism industry which accounts for nearly 70 per cent of GDP in Antigua and more than 10 per cent on most other islands.
The researchers estimate that a two degree C temperature rise in the Caribbean could, by the 2080s, triple the cases of dengue.
This AIACC study not only assessed the likelihood of dengue increasing but pin pointed measures that can reduce the risk.
It found, for example, that pupae of the dengue-carrying mosquito favour breeding in 40 gallon drums commonly used for outside water storage. The study also concluded that informal settlements and poor households, often headed by a single unemployed woman, were at greatest risk.
Education on the disease and its transmission, targeted at these households, is suggested as one important adaptation strategy, alongside measures to deal with the breeding grounds.
A pilot early warning system has also been developed and the findings and recommendations discussed with several countries including Jamaica and Trinidad and Tobago.