US wolf re-introduction still leaves aspens quaking


The re-introduction of wolves in a US National Park in the mid-1990s is not helping quaking aspens (Populus tremuloides) to become re-established, as many researchers hoped.

In a study published in the journal Ecology showed that the population of wolves in Yellowstone Park was not deterring elks from eating young trees and saplings.

It was assumed that the presence of wolves would create a “landscape of fear”, resulting in no-go areas for elks.

Researchers writing in the Ecological Society of America’s (ESA) journal said that the aspens were not regenerating well in the park as a result of the elk eating the young trees.

However, they added that the conventional wisdom suggested that as the wolves were predators of the elk, it was thought that the elk would eventually learn to avoid high-risk areas in which the wolves were found.

This would then allow plants in those areas – such as aspen – to grow big enough without being eaten and killed by the elk. And in the long-term, the thinking went, the habitat would be restored.

In this latest study, lead author Matthew Kauffman – a US Geological Survey scientist – suggested the findings showed that claims of an ecosystem-wide recovery of aspen were premature.

“This study not only confirms that elk are responsible for the decline of aspen in Yellowstone beginning in the 1890s, but also that none of the aspen groves studied after wolf restoration appear to be regenerating, even in areas risky to elk,” Dr Kauffman explained.

Because the “landscape of fear” idea did not appear to be benefiting aspen, the team concluded that if the Northern Range elk population did not continue to decline (their numbers are 40% of what they were before wolves), many of Yellowstone’s aspen stands were unlikely to recover.

“A landscape-level aspen recovery is likely only to occur if wolves, in combination with other predators and climate factors, further reduce the elk population,” observed Dr Kauffman.

The paper, Are wolves saving Yellowstone’s aspen? A landscape-level test of a behaviorally mediated trophic cascade, has been published online in Ecology. The authors of the paper are: Matthew Kauffman (USGS), Jedediah Brodie (University of Montana) and Erik Jules (Humboldt State University).

Source: ESA press release

Date: 01/09/2010

Dangerous climate change ‘to kill Amazon rainforest’


Global warming will wreck attempts to save the Amazon rainforest, reports the UK’s Guardian newspaper.

It says a study presented at a major climate science conference in Denmark has predicted that one-third of its trees will be killed by even modest temperature rises.

The research, by some of Britain’s leading experts on climate change, shows that even severe cuts in deforestation and carbon emissions will fail to save the emblematic South American jungle, the destruction of which has become a powerful symbol of human impact on the planet.

Up to 85% of the forest could be lost if spiralling greenhouse gas emissions are not brought under control, the experts said.

But even under the most optimistic climate change scenarios, the destruction of large parts of the forest is “irreversible”.

Vicky Pope, of the Met Office’s Hadley Centre, which carried out the study, said: “The impacts of climate change on the Amazon are much worse than we thought.

“As temperatures rise quickly over the coming century, the damage to the forest won’t be obvious straight away but we could be storing up trouble for the future.”

Tim Lenton, a climate expert at the University of East Anglia, called the study, unveiled at the University of Copenhagen gathering, a “bombshell”.

He said: “When I was young I thought chopping down the trees would destroy the forest, but now it seems that climate change will deliver the killer blow.”

The study, which has been submitted to the journal Nature Geoscience, used computer models to investigate how the Amazon would respond to future temperature rises.

It found that a 2C (3.6F) rise above pre-industrial levels, widely considered the best case global warming scenario and the target for ambitious international plans to curb emissions, would still see 20-40% of the Amazon die off within 100 years.

A 3C (5.4F) rise would see 75% of the forest destroyed by drought over the following century, while a 4C (7.2F) rise would kill 85%.

“The forest as we know it would effectively be gone,” Dr Pope said.

Experts had previously predicted that global warming could cause significant “die-back” of the Amazon.

The new research is the first to quantify the long-term effect.

Source: Guardian newspaper

Date: 12/03/2009

Quarter of PNG’s rainforests ‘lost to logging’


Nearly one quarter of Papua New Guinea’s rainforests were damaged or destroyed between 1972 and 2002, Mongabay.com reports.

Researchers, writing in the journal Biotopica, said the results – published in a report last June – show that Papua New Guinea is losing forests at a much faster rate than previously believed.

Over the 30-year study period, 15% of the nation’s tropical forests were cleared and a further 8.8% were degraded through logging.

“Our analysis does not support the theory that PNG’s forests have escaped the rapid changes recorded in other tropical regions,” the authors wrote.

“We conclude that rapid and substantial forest change has occurred in Papua New Guinea.”

Deforestation and forest degradation in Papua New Guinea are primarily driven by logging, followed by clearing for subsistence agriculture.

Since 2002 (a period not covered in the study), reports suggest that conversion of forest for industrial agriculture, especially oil palm plantations, has increased.

The study is based on comparisons between a land-cover map from 1972 and a land-cover map created from nationwide high-resolution satellite imagery recorded in 2002.

The authors found that most deforestation occurred in commercially accessible forest, where forest loss ranged from 1.1 to 3.4% each year.

Overall deforestation was 0.8 to 1.8% per year, higher than reported by the UN Food and Agriculture Organization (FAO), but lower than the rate of deforestation on neighboring islands, including Borneo and Sumatra.

Papua New Guinea’s primary forest cover fell from 33.23 million hectares to 25.33 million hectares during the 30-year period.

In the same period, almost 93 million hectares of forest were degraded by logging.

Lead author Phil Shearman, director of the University of Papua New Guinea’s Remote Sensing Centre, said that without incentives to keep forest standing, Papua New Guinea would continue to lose its forests.

“Forests in Papua New Guinea are being logged repeatedly and wastefully with little regard for the environmental consequences and with at least the passive complicity of government authorities,” Dr Shearman said.

He noted that nearly half of the country’s 8.7 million hectares of forest accessible to mechanised logging have been allocated to the commercial logging industry.

But he added that there may be hope because Papua New Guinea had become a leader in the push by tropical nations to seek compensation from industrialised countries for conserving forests as a giant store of carbon.

The mechanism known as REDD (Reducing Emissions from Deforestation and Degradation) could potentially provide billions of dollars for conservation, sustainable development and poverty alleviation.

“The government could make a significant contribution to global efforts to combat climate change,” observed Dr Shearman.

“It is in its own interest to do so, as this nation is particularly susceptible to negative effects due to loss of the forest cover.”

UN studies have show that coastal communities in Papua New Guinea are particularly at risk from climate change.
Source: Mongabay.com

Date: 23/02/2009

Double trouble for US hemlock forests


Hemlock forests in the east of the United States are under attack, according to Science Magazine’s ScienceNow website.

An aphid-like pest is ravaging the trees, while booming populations of deer devour other native plants.

Now, it reports, researchers have shown that the combination of these two threats adds up to even more trouble for the native ecosystem by creating the conditions that allow the establishment of invasive weeds.

Researchers first noticed the hemlock woolly adelgid (Adelges tsugae), a 1.5mm-long insect from Asia, in an arboretum near Richmond, Virginia, in 1951.

The bugs feed on starch in new twigs and can kill trees in just three years. As the hemlocks die, exotic plants such as garlic mustard (Alliaria petiolata) have been spreading and altering the habitat that native species require.

Anne Eschtruth, a graduate student in forest ecology at the University of California, Berkeley, wondered how the two phenomena were linked.

Two factors appear to be involved. First, by defoliating the forest canopy, the adelgids allow more light to reach the forest floor.

This promotes the growth of native and exotic plants, Ms Eschtruth and colleagues report online in Conservation Biology.

The second factor is white-tailed deer (Odocoileus virginianus). Following anecdotal reports that the deer sometimes prefer to eat one kind of plant over another, the researchers studied the animals’ behavior in 10 forests in north-eastern Pennsylvania and western New Jersey from 2003 to 2006.

They fenced off 40 patches of forest so that deer could not feed there. In these enclosures, the invasive plants grew about as well as the native plants did.

But where deer were able to graze, the exotics did better than the natives; the more deer there were, the more the invaders thrived.

One reason could be that additional sunlight causes native and exotic plants to put more resources into growing stems and leaves rather than roots, which would make them more vulnerable to browsing.

As are result, savory natives, favoured by the deer, would suffer more from large deer populations, while uneaten exotics would benefit.

“These effects are happening right around us and appear to be increasing with mounting deer densities and woolly adelgid expansion,” says plant ecologist Don Waller of the University of Wisconsin, Madison.

The findings suggest that land managers need to consider weed invasions, deer overpopulation, and tree health together rather than as separate issues.

And, he adds, reducing deer populations could be an effective way of combating exotic plants.

Source: ScienceNow website

Date: 19/12/2008

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