Climate impact on plants could be underestimated - study

AFP Yahoo News 3 May 12;

Experiments that try to simulate global warming's impact on plants badly underestimate what happens in the real world, according to a study published on Wednesday in the journal Nature.

The investigation backs anecdotal evidence from farmers and gardeners, especially in the northern hemisphere, who say seasonal plants are stirring into life far earlier than in the past.

Artificial experiments into global warming usually entail encasing a plant in an open-top greenhouse-like chamber, or in a canopy that has a small heater in its roof, in order to replicate rising temperature.

These experiments have determined that flowering and leafing occur between 1.9 and 3.3 days earlier for every one degree Celsius (1.8 degrees Fahrenheit) in temperature increase.

But the study says the true figure is far higher.

Plants start to grow leaves and flowers between 2.5 and five days earlier per one degree C (1.8 F), it says.

It bases this on a comparison between warming experiments on 1,634 plant species and long-term observations of these species in the wild, carried out by some 20 institutions in North America, Japan and Australia.

"Up to now, it's been assumed that experimental systems will respond the same as natural systems respond -- but they don't," co-author Benjamin Cook of the Lamont-Doherty Earth Observatory at Columbia University, New York, said in a press release.

The experimental methods may be flawed because they reduce light, wind or soil moisture, all of which affect the plant's seasonal maturation, says the paper.

From 1906 to 2005, global surface temperatures rose by 0.74 C (1.33 F), according to the UN's Intergovernmental Panel on Climate Change (IPCC) in its 2007 Fourth Assessment Report.

On present trends of heat-trapping carbon emissions, Earth is on track for additional warming of two degrees Celsius (3.6 F) or more, according to estimates published by other sources last year.

Some experts deem those estimates conservative and note many locations are warming far faster than the global average.

"The meticulously recorded and celebrated blooming of Washington DC's cherry blossoms has advanced about a week since the 1970s," said the press release, issued by Columbia University's Earth Institute.

"If the trend continues, some recent projections say that by 2080 they will be coming out in February."

Plant Study Flags Dangers Of Warming World
Nina Chestney PlanetArk 3 May 12;

Plant Study Flags Dangers Of Warming World Photo: Kieran Doherty
A bee collects pollen from a field of crocuses at Kew Gardens in London, March 17, 2005.
Photo: Kieran Doherty

Plants are flowering faster than scientists predicted in response to climate change, research in the United States showed on Wednesday, which could have devastating knock-on effects for food chains and ecosystems.

Global warming is having a significant impact on hundreds of plant and animal species around the world, changing some breeding, migration and feeding patterns, scientists say.

Increased carbon dioxide concentration in the atmosphere from burning fossil fuels can affect how plants produce oxygen, while higher temperatures and variable rainfall patterns can change their behavior.

"Predicting species' response to climate change is a major challenge in ecology," said researchers at the University of California San Diego and several other U.S. institutions.

They said plants had been the focus of study because their response to climate change could affect food chains and ecosystem services such as pollination, nutrient cycles and water supply.

The study, published on the Nature website, draws on evidence from plant life cycle studies and experiments across four continents and 1,634 species. It found that some experiments had underestimated the speed of flowering by 8.5 times and growing leaves by 4 times.

"Across all species, the experiments under-predicted the magnitude of the advance - for both leafing and flowering - that results from temperature increases," the study said.

The design of future experiments may need to be improved to better predict how plants will react to climate change, it said.

Plants are essential to life on Earth. They are the base of the food chain, using photosynthesis to produce sugar from carbon dioxide and water. They expel oxygen which is needed by nearly every organism which inhabits the planet.

Scientists estimate the world's average temperature has risen by about 0.8 degrees Celsius since 1900, and nearly 0.2 degrees per decade since 1979.

So far, efforts to cut emissions of planet-warming greenhouse gases are not seen as sufficient to prevent the Earth heating up beyond 2 degrees C this century - a threshold scientists say risks an unstable climate in which weather extremes are common, leading to drought, floods, crop failures and rising sea levels.

The study can be viewed at www.nature.com/nature