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Wednesday, January 4, 2012

Species biodiversity under threat from the velocity of climate change

Scientists have been able to calculate the velocity of climate change on land and ocean environments using temperature records to determine isotherms and their change in a fifty year period from 1960 to 2009. So how fast are climate envelopes moving? The general median answer is 27.3 km/decade on land, and 21.7 km/decade in the ocean. This equates to a speed needed to outrun climate change on land (2.7 kilometers per year) and in the oceans (2.2 kilometers per year). This rate of movement of thermal climate envelopes poses problems for species facing a high speed migration, or a difficult and abrupt adaptation or extinction.

Here is how scientists measured the velocity of climate change ocurring:

We used global surface temperatures over 50 years (1960-2009) to calculate the distribution of the velocity and seasonal shifts of isotherm migration over land and ocean on a 1°-by-1° grid. The velocity of climate change (in km/year) was calculated as the ratio of the long-term temperature trend (in °C/year) to the two-dimensional spatial gradient in temperature (in °C/km, calculated over a 3°-by-3° grid), oriented along the spatial gradient. We introduced the seasonal climate shift (in days/decade) as the ratio of the long-term temperature trend (°C/year) to the seasonal rate of change in temperature (°C/day). We present seasonal shifts for spring and fall globally using April and October temperatures.

For terrestrial species this involves migration polewards or to a greater altitude. For species that live on the top of mountains, ecosystem islands in the sky, they face a grim future of adapting to a warmer environment or extinction as they compete with species moving up from lower altitudes.

But even for those species with the ability to migrate further north in the northern hemisphere, or south in the southern hemisphere, there are often large and substantial obstacles to hinder and prevent migration. Our cites and towns with criss-crossing patterns of railways and roads, our farms and mastery of agricultural land has cornered many species in isolated reserves and nature parks with remnant ecosystems often with no congruent ecosytem links to related ecosystem areas to allow species to migrate to follow their climate envelope. These species face a grim future of crossing hostile man-made landscapes to stay within their climate envelope or adapt to the changing climate in their island reserves with a high risk of extinction.

Birds with their agile mobility will probably fair better at migration than ground dwelling creatures, but plants will face enormous difficulties in relocating with the changed climate conditions. In mountainous areas some plants may survive by migrating further up the mountain, but for flora on plains it may prove extremely difficult to match the pace of climate change.

If there are Ents in this world, as there were in JRR Tolkien's fantasy of Middle-Earth, now is the time we need them to awake and shepherd the forests and plant communities to match the velocity of climate change.

Velocity of climate change imperiling ocean diversity

The problems are just as severe for marine organisms. As temperatures change in the oceans, the creatures of the sea will tend to migrate towards the Arctic and Antarctic poles. A few creatures may also be able to adapt by going to slightly greater ocean depths.

The scientists also discovered that organisms tended to move to the poles with a displacement of a tilt of 12 degrees, if they were not otherwise obstructed.

"Most scientific and public attention regarding the impacts of climate change on our planet have paid attention to how biodiversity and people are being affected on land," Benjamin Halpern, research scientist at NCEAS and a co-author of the paper, said in a media release. "Yet most of our planet is ocean, and people depend on and benefit from the ocean for all sorts of things, such as seafood to eat or wildlife to watch (like whales).

"Our study looks at how climate change is affecting the oceans, focusing on the velocity of change that shifts where species exist, how well they can persist, and whether or not species will be able to keep up with that change," said Halpern, who is also director of University of California Santa Barbara's Center for Marine Assessment and Planning. "Our results provide a road map of sorts on where species need to move to adapt, and how fast."

The paper says "depth changes have been reported for only a few marine organisms, such as fish and hydroids. For species that cannot adjust their depth, range shifts may be limited by the availability of suitable habitat. Where such habitat is not aligned with the velocity of climate change, as happens on east-west coastlines, the velocity along the axis of the habitat could be much faster."

Sea surface temperatures have increased at a much slower rate to land temperatures, due to currents tending to reduce small-scale variability in ocean surface temperatures. The resulting "median velocity of isotherms across the ocean (21.7 km/decade) is 79% of that on land (27.3 km/decade), but when comparing only those latitudes where both land and ocean are present (50°S to 80°N), velocities in the ocean (27.5 km/decade) are similar to those on land (27.4 km/decade)." This equates to a speed needed to outrun climate change on land (2.7 kilometers per year) and in the oceans (2.2 kilometers per year).

"Not a lot of marine critters have been able to keep up with that," said paper co-author John Bruno, a marine ecologist at the University of North Carolina at Chapel Hill. "Being stuck in a warming environment can cause reductions in the growth, reproduction, and survival of ecologically and economically important ocean life such as fish, corals, and sea birds."

There are also cooling areas like in the Southern Ocean and Eastern Boundary Current regions with increased upwelling. "With climate change we often assume that populations simply need to move poleward to escape warming, but our study shows that in the ocean, the escape routes are more complex," said ecologist Lauren Buckley of the University of North Carolina at Chapel Hill, also a co-author of the paper. "For example, marine life off the California coast would need to move south to remain in its preferred environment due to increased upwelling."

In the sub-Arctic and within 15° of the equator the velocity of climate change two to seven times faster in the ocean than on land, while ocean and land velocities are similar at most other latitudes (20° to 50°S and 15° to 45°N).

"Some of the areas where organisms would need to relocate the fastest to stay ahead of climate change are important biodiversity hot spots, such as the coral triangle region in southeastern Asia," said lead author Michael Burrows of the Scottish Association of Marine Science.

The World Wildlife Fund (WWF) commissioned a report in 2008 on the Coral Triangle and Climate change. The research was lead by Professor Ove Hoegh-Guldberg and identified that Coral reefs could disappear entirely from the Coral Triangle region of the Pacific Ocean by the end of the century, threatening the food supply and livelihoods for about 100 million people in the region.

The Coral Triangle is home to more than one third of all the world's coral reefs, including over 600 different species of reef-building coral and 3,000 species of reef fish.

The paper concludes

"Despite slower ocean warming, the velocity of climate change and seasonal shift in the ocean are as high as on land and often deviate from simple expectations of poleward migration and earlier springs/later falls. Direct effects of climate warming are therefore likely to be as great in the oceans as on land at comparable latitudes and greater around the equator. Maps of the velocity of climate change and seasonal shift show the areas where the threat to biodiversity from organisms' need to rapidly track thermal conditions by shifting distributions and retiming seasonal thermal events may be greatest; these areas may coincide with high biodiversity, especially in the oceans."

Faster velocities off Western Australia coast

University of Western Australia Oceans Institute director Professor Carlos Duarte who worked on the climate velocity study said that Western Australia (WA) has a velocity of climate change much higher than average - in the order of 50-70km per year.

Across the globe there is an enormous range in the velocity, "from almost nil in some areas to 200km per year in others". said Professor Duarte. "It is possible that some organisms have already been left behind,"

Slow moving or sessile organisms such as coral or sponges must adapt to the warming temperature or face the threat of extinction.

Organisms that can match the speed of climate change may also be blocked by landmasses as they try to move towards the poles. "For instance, organisms in the coral triangle off the coast of Australia (in the waters of New Guinea, Indonesia and the Solomon Islands) encounter the Australian land mass as they head for Antarctica." said Professor Duarte.

Australian Seaweed species being pushed to the brink

A study published in Current Biology on November 8, 2011 - Seaweed Communities in Retreat from Ocean Warming - examined the impact of warming ocean on seaweed communities in southern Australian waters.

According to research led by Assistant Professor Thomas Wernberg from The University of Western Australia's Ocean's Institute, modern seaweed communities to the south are becoming more similar to past communities in the north, with several temperate species moving poleward (south). The results predict that up to one quarter of species in southern Australian waters might retract towards extinction.

The researchers found changes in seaweed communities in both the Indian and Pacific Oceans, consistent with rapid warming over the past decades.

"We found that continued warming might drive potentially hundreds of species towards the edge of the Australian continent beyond which there is no refuge," Assistant Professor Wernberg said.

The researchers believe while some species may be able to make some adjustments to cope with natural cooling and warming cycles, the predicted rate and strength of warming in the coming decades is likely to force many retreating species further south and beyond the limits of available habitat.

"The potential for global extinctions is concerning because one quarter of all macroalgal species in the world are found off Australia and these marine habitats support equally unique fish and invertebrate communities," Assistant Professor Wernberg said.

The velocity of climate change points to Oceans at high risk of unprecedented Marine extinction as scientists warn with Coral Reefs and Ocean Biodiversity threatened by Climate Change.

Marine scientists have also consistently warned of another high profile marine chemistry problem: Ocean Acidification Accelerating; Severe Damages Imminent. You can watch 2 videos on ocean acidification: Acid Test and a presentation by marine chemist Andrew Dickson. Marine scientists also appealed to climate negotiators at Durban in December 2011 to act on reducing CO2 emissions to reduce Ocean Acidification.


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