Forests make heatwaves ‘initially warmer’

During heatwaves forests reduce their evaporation, causing the atmosphere to warm up even more, say researchers.

During extremely long periods of heat, however, this reduction enables the forests to continue their evaporation for longer, so the net effect is ultimately one of cooling in relation to the surroundings, explained a team of scientists led by Ryan Teuling from Wageningen University in the Netherlands.

Writing in the journal Nature Geoscience, Dr Teuling worked on the investigation in collaboration with climate researchers from a number of European countries.

The study was prompted by recent heatwaves in Europe, which had raised interest in questions about the influence of land use on temperatures and climate.

Up to now, scientists had assumed that a lack of precipitation during heatwaves automatically led to a reduction in evaporation.

That reduction was thought to be less for forests, because trees, with their deeper root systems, have more water available to them. Examination of the precise role of land use, however, has been largely neglected up to now.

The study found large differences in evaporation strategies during heat waves. Grasslands evaporate more at higher temperatures and stop only when no more water is available.

Forests, in contrast, respond to higher temperatures by evaporating less, which leaves more water at their disposal.

During brief heatwaves, therefore, the greatest warming is found above forests, but during prolonged heat waves the increased evaporation of grasslands ends up causing a shortage of water.

This can lead to exceptionally high temperatures, such as those measured in France in the summer of 2003.

This mechanism might also offer an explanation for the unusually high temperatures near Moscow this summer, the researchers suggest.

In these types of extreme situations, forests in fact have a cooling effect on the climate.

The research was done on the basis of observations made above forests and grasslands in Europe by an extensive network of flux towers. For areas without towers, satellite data were used.

Source: Wageningen University press release

Date: 06/09/2010

Firm to trial bleeding canker ‘cure’

Arboriculture specialists may have found a cure for bleeding canker in horse chestnut trees, Horticulture Week reports.

It says arboculturalist consultancy Jonathan Cocking Associates (JCA) will trial a newly patented product with English Heritage.

JCA managing director Jonathan Cocking said he was trademarking the product, which kills canker bacterium in trees’ vascular systems.

Plugs of bark are removed around the chestnut, he explains, and a tree infusion is screwed into the holes.

The process takes an hour and after a year the tree refoliates, he adds.

“We are rolling it out with a few high-profile programmes including one with English Heritage.

“The treatment is invasive, but it’s a natural product.

“It’s better to get cracking and save a few trees than run a 10-year study programme only to find at the end of it that all the horse chestnuts have died.”

JCA, based in Halifax, West Yorkshire, has worked with a Dutch firm on the cure and hopes to license the product later in 2009.

Source: Horticulture Week

Date: 16/01/2009

UK research centre to host European forestry climate hub

A UK research centre is set to become the European hub for an ambitious global research programme into the impacts of climate change on forests, the Centre for Ecology and Hydrology (CEH) has announced.

In a press release, the CEH said its Wytham Woods centre, near Oxford in south-east England, will base environment charity Earthwatch’s Europe Regional Climate Centre.

Earthwatch, an environmental charity, has announced the opening of its Europe Regional Climate Centre as part of the HSBC Climate Partnership.

The centre, funded by the Hong Kong-based bank HSBC’s Cimate Partnership, will undertake a five-year climate change and forestry research programme.

The scheme is a partnership between Earthwatch, CEH and two local partner groups: Oxford University’s Environmental Change Institute (ECI) and its Wildlife and Conservation Research Unit (WildCRU).

The centre’s researchers will examine numerous aspects of forest ecology; from the flow of carbon within woodlands, to the response of small mammals and insects to changes in weather patterns.

Over the five years, the team is expected to complete 40,000 hours of fieldwork, which CEH says is equivalent to 21 years work for a single scientist.

The new centre is one of five throughout the world. The others are located in Brazil, India, China and North America.

Source: CEH press release

Date: 18/08/2008

Statistic: European forest fires

Fire is the main cause of forest destruction in the countries of the Mediterranean Basin, says the Food and Agriculture Organization (FAO).

Amazingly, about 50,000 fires sweep through 700,000 to one million hectares of Mediterranean forests, other wooded land and other land each year.

As well as causing enormous economic damage, the fires result in massive ecological loss and human deaths.

Forest fires in the Mediterranean Basin are significantly determined by predominant climatic conditions.

Prolonged summers (extending from June to October and sometimes even longer), with virtually no rain and average daytime temperatures well in excess of 30C, reduce the moisture content of forest litter to below 5%.

Under these conditions, even a small addition of heat (lightning, a spark, a match, a discarded cigarette butt) can be enough to start a fierce fire.

Source: FAO Mediterranean Basin forest fire workshop paper

Date: 06/08/2008

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