NatureWatch: When the living isn’t easy

Scientists continue to discover how the plants and animals around us are struggling to survive in some pretty hostile environments. Sadly, that’s sometimes partly our fault. Here are four recent stories of hard living.

The threat to the sky islands

As temperatures rise, it’s tempting to move to higher ground, but what if you have nowhere to go? Colombian researchers have completed the first intensive study of the Páramo regions of the Andes, to assess their vulnerability to climate change and human activities.

These so-called sky islands are above the tree line but below the permanently frozen mountaintops. Despite extreme variations in temperature, water availability and sunlight, there are now more than 3000 plant species throughout the South American Páramos, and they are considered to be among the fastest evolving ecosystems in the world.

But they are also among the most threatened, says Andrés Cortés, of the Colombian Corporation for Agricultural Research, who led the research published in the journal Frontiers in Ecology and Evolution.

His team selected Espeletia as a representative genus because it is one of the most diverse and successful plant genera endemic to the Páramos, as well as iconic with its unbranched trunk topped with a rosette of leaves.

They used computer modelling to predict what the distribution of 28 species of Espeletia would look like in 2050, adding in factors such as nature reserves, surrounding forests, population density, agriculture and mining.

They found that some Páramos were particularly vulnerable, and confirmed the limited opportunities for Espeletia species to migrate or adapt.

“Páramos are also the main water supplier of wetland ecosystems and densely populated areas, hence disregarding the future of the Páramos may jeopardise overall food and water safety in the northern Andes,” Cortés says.

The small guys struggle too

Still in South America, but at a much smaller scale, 27 researchers from six nations have explored what life’s like for insect larvae and other small organisms in freshwater ecosystems.

Exploring the tank (the centrally-located water-holding cup) of bromeliad plants in conditions of flooding and drought, they discovered, they say, that small organisms at the bottom of the food chain suffer the most from rainfall instability.

Conventional wisdom is that larger animals are most affected by climate changes, says Gustavo Quevedo Romero from Brazil’s IB-UNICAMP, but “we showed that in this case the bottom of the food chain may be more sensitive, and changes there can modify the trophic levels above”.

The researchers were surprised to find a single consistent pattern of susceptibility to climate change across seven geographically and climatically diverse study sites: predators always benefited from drier conditions, they say, while small organisms were adversely affected in small environments and favoured in larger environments with more rainfall.

They say their findings, reported in Nature Communications, suggest climate change causes instability in food webs, especially when it is associated with drought.

“More predators in a bromeliad with less water intensify the top-down predation effect on prey communities,” says Romero. “This destabilises the food web and may lead to local extinction of both predator and prey species.”

Arctic trees struggle with pollution

As far from South America as you could imagine, in more ways than one, researchers have found that decades of nickel and copper mining in the Russian Arctic have not only devastated the trees, they have affected the global carbon cycle.

An international team led by the University of Cambridge, UK, analysed tree rings from Norilsk in Siberia – the world’s northernmost city – and found, they say, that the effects of industrial pollution are far worse and more widespread than previously thought.

High pollution levels cause declining tree growth, which affects the amount of carbon that can be sequestered in the boreal forest.

“What surprised us is just how widespread the effects of industrial pollution are: the scale of the damage shows just how vulnerable and sensitive the boreal forest is,” says Ulf Büntgen, lead author of a paper in Ecology Letters.

The link between pollution and forest health is well-known, the researchers say, but it has not been able to explain the “divergence problem in dendrochronology” – a decoupling of tree ring width from rising air temperatures seen since the 1970s.

They combined ring width and wood chemistry measurements from living and dead trees with soil characteristics and computer modelling to reconstruct the history and intensity of Norilsk’s forest dieback and show that “Arctic dimming” since the 1970s has substantially reduced tree growth.

Arctic dimming is caused by increased particulates in the Earth’s atmosphere, whether from pollution, dust or volcanic eruptions. The phenomenon partially blocks out sunlight, slowing the process of evaporation and interfering with the hydrological cycle.

Global warming should be expected to increase the rate of boreal tree growth, but the researchers found that as the pollution levels peaked, the rate of growth in northern Siberia slowed. Pollution levels diminished their ability to turn sunlight into energy through photosynthesis.

Still growing in the dark

Putting up a good fight are microscopic marine algae of the Arctic which, a new study has found, can grow even in virtual darkness beneath the thick winter sea ice.

It’s only slight growth, it must be said, but still it contradicts the popular belief that phytoplankton cannot begin growing until the sea ice starts to melt. Instead, the researchers suggest, algae have adapted to grow under the extreme winter conditions, culminating in an explosive summer bloom.

In fact, over two years of study in Baffin Bay, which lies between Canada and Greenland, they found that phytoplankton reached its peak accumulation rate in April and May, two months before the ice began to retreat.

Scientists have found it difficult to observe algae blooms beneath the ice, and when they have, they tended to attribute the blooms to light shining through melted areas in the icy surface.

To overcome this, the team from Canada, France, China and Japan, led by Achim Randelhoff from the Takuvik Joint International Laboratory, deployed four floats – each equipped with an ice avoidance system – to measure annual fluctuations in the tiny marine algae using particle backscattering and chlorophyll.

The findings are published in Science Advances.