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Grassland lab raises species loss alarm

Field experiment on a special area of US grassland shows how climate change could disrupt the delicate life cycle of ecosystems.

LONDON, 20 March, 2017 – Scientists in California who turned a patch of natural grassland into a laboratory have established a subtle link between flowering times and the mix of species in an ecosystem – indicating that global warming could change planetary biology and disrupt ecosystems in hitherto unsuspected ways.

And since the life cycle of the honeybees, the arrival of the migrant birds, the bloom of flowers and the setting of fruit is dependent on climatic stability, any change could have uncomfortable consequences − first for the natural systems that maintain the management of air and water and waste disposal, and then for human economies that depend on natural services.

The Coyote Ridge testbed for the Californian experiment – reported in the Proceedings of the National Academy of Sciences – was an unusual geological soil structure known as serpentine grassland.

Important grassland

This is a stretch of land rich in the mineral serpentine, or magnesium silicate, and hostile to many species.

But such grassland represents an important US ecosystem, and a tidy laboratory for researchers engaged in the science of phenology – the measurement of such recurring natural phenomena as first bud, first flower, first fruit, first leaf fall.

And since global warming driven by human combustion of fossil fuels has begun to change climates in the Arctic and temperate zones, with spring arriving dramatically earlier in many places, phenology is a measure of global change.

The experiments were, in essence, simple. Since changes in flowering time could affect the life cycles of other species, could changes in species affect flowering times?

The researchers removed a number of species from the mix on the serpentine grassland plot in California, and found that the flowering times of the remaining species also altered.

“Losing species from an ecosystem made
the remaining species flower earlier, and that’s
the same effect that climate change has”

In theory, this could create problems for those insects, birds and mammals that depend directly or indirectly on the flower species.

Professor Erika Zavaleta, an ecosystem ecologist at the University of California Santa Cruz, says: “We found that losing species from an ecosystem made the remaining species flower earlier, and that’s the same effect that climate change has. Adding one on top of the other could push apart the timing of previously synchronised events even more than expected.”

This is bedrock research in more than one sense: by simplifying an ecosystem, researchers hope to learn more about the ways creatures react with each other, and with a changing climate.

Shifts in timing have consequences – for instance, some wildlife relationships have been disrupted, while plants have been observed to migrate to new locations or to change their timetables in response to milder winters.

The US, with its huge range of climate and terrain, has become a phenological experiment on a continental scale, with change recorded in the Rockies mountain range and even around Walden Pond in Massachusetts, the stretch of water celebrated by the 19th-century naturalist and writer, Henry David Thoreau.

Biodiversity shifts

The challenge is now to make detailed sense of the changes triggered by climate change and biodiversity shifts. Are they driven by moisture, soil temperature, or the availability of nitrogen? Or something else?

The answers matter. The natural timetable change linked to the loss of just two species from the test plot was roughly the same as the average change in one decade of global warming.

“We are losing species at such a fast rate these days, it raises the question of how these effects cascade through an ecosystem and affect the ecology and evolution of what’s left,” Professor Zavaleta says.

“This study reveals a new pathway by which species loss can affect the dynamics of an ecosystem.

“It opens up the possibility that biological timing is going to respond in unexpected ways to the onslaught of different stresses that natural systems are experiencing, and the responses could be bigger than expected.” – Climate News Network