Posts Tagged ‘conservation’

Amazon trees vulnerable to fire and climate combination

By Mark Kinver
Environment reporter, BBC News

An increase in the frequency of fires and drought-like conditions could result in an ecological tipping point

The combination of fire and extreme weather could accelerate tree mortality in the Amazon, a study has suggested.

Researchers said field experiments showed that severe droughts could trigger dieback of forests in the near-term.

Efforts to curb deforestation needed to be accompanied by initiatives to stop land management fires spreading into adjoining forest reserves, they added.

The findings appear in the Proceedings of the National Academy of Sciences.

Co-author Paulo Brando, a researcher from Brazil’s Amazon Environmental Research Institute and the Woods Hole Research Center, US, explained that the findings were based on data gathered from a long-running field experiment, described as the first of its kind.

In 2004, the team established three plots in the south-east Amazon – one of which was burned annually, another was burned every three years, while the remaining one was left untouched as a control plot.

Aerial photo of experimental plots: annual burn (left); burned every three years (centre) and unburned/control (right). The dashed line indicates the forest edge/interior zone (Image: P.Brando/PNAS)

“If we burned every year, we did not have enough fuel (leaves and trees) to drive a high intensity fire – fires that will kill a lot of trees – so we published a few papers saying that this kind of forest was quite fire resistant,” explained Dr Brando.

An increase in the amount of sunlight reaching the ground raised the forest’s ambient temperature

But he told BBC News that the team was surprised in 2007: “We burned both plots (fourth burn for the annual plot and second burn for three-year plot) and both plots responded really strongly to the fires.

“There was a shift in the system from a forest to a savannah-like environment… grasses were invading the forest and there were fundamental changes within the ecosystem.

He added that drought conditions during that year triggered the change: “There were more leaves and twigs on the ground, they were drier so the fires were quite intense.

“To our surprise, the major effects were not observed in the plot we burned every year but rather in the one we burned every three years.

“This was because there was more time for fuel accumulation, and also it was because the productivity of that plot was still quite high, whereas in the [annual burn] plot, the fuel was being removed every year and the productivity of the system was reduced.”

Changing landscape

Dr Brando said the abrupt high tree-mortality rates had a lasting impact on the landscape as grasses invaded the space once occupied by trees.

“You do not need drought anymore to observe high density fires because grasses can accumulate way more fuel than the native, wood vegetation,” he explains.

As well as observing the loss of a number of tree species, Dr Brando said there were wider ecological consequences as a result of losing tree cover.

“Burned plots were four degrees warmer because they had fewer leaves and less capacity to cool down the system through photosynthesis,” he observed.

“So we have seen major changes, not only in species composition but in the functionality of the forest as well; it cycles less water because it is warmer and stores less carbon.”

Climate models suggest that the probability of severe droughts in the region are likely to be much more common by the end of the century.

Amazon sunrise © SMG

Amazon sunrise © SMG

At an international conference held at the University of Oxford in 2012, researchers presented findings that suggested tropical forests in Africa could be more resilient to future climate change than the Amazon and other forested regions.

Scientists at the gathering concluded that tree species in Africa’s tropical forests had endured a number of climatic catastrophes over the past 4,000 years.

During that period, the African forests had lost species that would have been potentially vulnerable, while the remaining species were “relatively adaptable… to quite rapid changes in rainfall,” explained conference organiser Yadvinder Malhi, from the university’s Environmental Change Institute.

Responding to Dr Brando’s findings, Prof Malhi said: “Much of current scientific opinion suggests that intact tropical forests may be quite resilient to climate change, but the combination of climate change, land-use change and fire may be much more destructive.

Prof Malhi, who was not involved in the study, added that these ideas have rarely been demonstrated in practice.

“What is unique about this study – a long-term experiment that took a lot of stamina and persistence to implement – is that it directly demonstrates the effects of this deadly combination of factors, and enables exploration of the details of the ecological processes and interactions involved,” he told BBC News.

Here’s a short clip of some of the Amazon’s most endangered monkeys.

Mineral hints at bright blue rocks deep in the Earth

By Simon Redfern BBC Science writer

Blue planet: Ringwoodite minerals reveal hints of what things might look like deep within the Earth

Minerals preserved in diamond have revealed hints of the bright blue rocks that exist deep within the Earth.

They also provide the first direct evidence that there may be as much water trapped in those rocks as there is in all the oceans.

The diamond, from central-west Brazil, contains minerals that formed as deep as 600km down and that have significant amounts of water trapped within them.

Researchers have published their findings in the journal Nature.

The study suggests water may be stored deep in the interiors of many rocky planets.

Diamonds, brought to the Earth’s surface in violent eruptions of deep volcanic rocks called kimberlites, provide a tantalising window into the deep Earth.

A research team led by Prof Graham Pearson of the University of Alberta, Canada, studied a diamond from a 100-million-year-old kimberlite found in Juina, Brazil, as part of a wider project.

They noticed that it contained a mineral, ringwoodite, that is only thought to form between 410km and 660km beneath the Earth’s surface, showing just how deep some diamonds originate.

Buried oceans
While ringwoodite has previously been found in meteorites, this is the first time a terrestrial ringwoodite has been seen. But more extraordinarily, the researchers found that the mineral contains about 1% water.

While this sounds like very little, because ringwoodite makes up almost all of this immense portion of the deep Earth, it adds up to a huge amount of deep water.

Dr Sally Gibson from the University of Cambridge, who was not involved in the work, commented: “Finding water in such large concentrations is a hugely significant development in our understanding of the ultimate origin of water now present at Earth’s surface.”

Ringwoodite is thought to form between 410km and 660km beneath the Earth’s surface

The observation is the first physical evidence that water can be stored in the deep interiors of planets and solves a 25-year-old controversy about whether the deep Earth is dry, wet, or wet in patches.

Discussing his findings, Prof Pearson told BBC News: “The discovery highlights the unique value of natural diamonds in trapping and preserving fragments of the deep Earth.

“It’s incredible to think that, as you hold this sample in your hand, the residual pressure at the interface between the diamond and the inclusion is 20,000 atmospheres.”

Describing his diamond sample, he said: “It looks like it’s been to hell and back, which it has.”

Blue planet
Prof Joseph Smyth of the University of Colorado has spent many years studying ringwoodite and similar minerals synthesised in his laboratory.

He said: “I think it’s stunning! It implies that the interior may store several times the amount of water in the oceans. It tells us that hydrogen is an essential ingredient in the Earth and not added late from comets.

The Brazilian diamond was sculpted by corrosive fluids on its way up to the surface

“This discovery implies that hydrogen may control the interior processes of the Earth just as it controls the surface processes, and that water planets, like Earth, may be common in our galaxy.”

A key question posed by the observation is to understand the extent to which plate tectonics on Earth leads to oceans of water being recycled deep within our planet, and to predict the likely amounts of water trapped in other rocky planets.

Ringwoodite is expected to form deep in Mars as well, for example, where it sits against the metallic core.

Grains of the same mineral synthesised in Prof Smyth’s laboratory shine bright blue under the microscope.

Given the new findings of ringwoodite’s water-bearing capabilities, its abundance at depth, and its beautiful hue, the term “blue planet” seems even more appropriate for Earth.



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