Global warming creeps across the world at a speed of a quarter of a
mile each year, according to a new study that highlights the problems
that rising temperatures pose to plants and animals. Species that can
tolerate only a narrow range of temperatures will need to move as
quickly if they are to survive. Wildlife in lowland tropics, mangroves
and desert areas are at greater risk than species in mountainous areas,
the study suggests.
"These are the conditions that will set the stage, whether species move or cope in place," said Chris Field, director of the department of global ecology at the Carnegie Institution in the US, who worked on the project. "Expressed as velocities, climate change projections connect directly to survival prospects for plants and animals."
The study, by scientists at the Carnegie Institution, Stanford University, the California Academy of Sciences, and the University of California, Berkeley,
combined information on current and projected future climate to
calculate a "temperature velocity" for different parts of the world.
They
found that mountainous areas will have the lowest velocity of
temperature change, meaning that animals will not need to move very far
to stay in the temperature range of their natural habitat. However,
much larger geographic displacements are required in flatter areas such
as flooded grasslands, mangroves and deserts,
in order for animals to keep pace with their climate zone. The
researchers also found that most currently protected areas are not big
enough to accommodate the displacements required.
Healy Hamilton,
director of the centre for applied biodiversity informatics at the
California Academy of Sciences, said: "One of the most powerful aspects
of this data is that it allows us to evaluate how our current protected
area network will perform as we attempt to conserve biodiversity in the
face of global climate change."
He added: "When we look at
residence times for protected areas, which we define as the amount of
time it will take current climate conditions to move across and out of
a given protected area, only 8% of our current protected areas have
residence times of more than 100 years. If we want to improve these
numbers, we need to both reduce our carbon emissions and work quickly
towards expanding and connecting our global network of protected areas."
The study found that global warming would have the lowest velocities in tropical and subtropical coniferous forests, where it would move at about 80 metres a year, and montane grasslands and shrublands - a biome with grass and shrubs at high elevations - with a projected velocity of about 110 metres each year.
Global
warming is expected to sweep more quickly across flatter areas, such as
mangrove swamps and flooded grasslands and savannas, where it could
have velocities above 1km a year. Across the world, the average
velocity is 420 metres each year. The results are published in the journal Nature.
Wildlife
in areas with low projected climate change velocities are not
necessarily better protected, the scientists point out. Habitats such
as broadleaf forests are often small and fragmented, which makes it
harder for species to move.
The study examines the movement of
climate zones, not species, the scientists stress, which means it is
difficult to predict what the impacts may be on individual trees,
insects and animals. Some are more tolerant to changing temperature
than others, and the movement of species can be difficult to track.
While trees are estimated to have spread northwards through a warming
Europe after the end of the last ice age at a speed of about 1km per
year, this could be down to dormant seeds reseeding the landscape,
which would not be possible if species are forced to shift to new
territories.
The scientists say that global warming will cause
temperatures to change so rapidly that almost a third of the globe
could see climate velocities higher than even the most optimistic
estimates of plant migration speeds.
Some plants and animals may
have to be physically moved by humans to help them cope, the scientists
say, while protected areas must also be enlarged and joined together.
