By Tim Radford
Trees may be getting more efficient in the way they manage water. They could be exploiting the higher levels of carbon dioxide in the atmosphere, growing foliage from a lower uptake of groundwater. If so, then the carbon dioxide fertilization effect—predicted by theorists and observed in laboratory experiments—could be real.
This is a provisional finding, because it is pretty difficult to measure the precise economy of a whole forest or an open wilderness.
But Trevor Keenan—of Macquarie University in Australia and Harvard University in the U.S.—and colleagues report in Nature that they used an indirect measure, called the eddy-covariance technique, to monitor the way managed forests handle two important gases: carbon dioxide and water vapor.
Carbon dioxide levels in the atmosphere were once 280 parts per million; they are now 400 ppm and still rising. For more than 20 years, rigs have towered above the world’s forests recording eddy-covariance, measuring carbon uptake and water-use over areas of a square kilometer.
Keenan and his fellow-researchers looked at the data from 21 temperate and boreal forests in the northern hemisphere and found a remarkably consistent trend: As the years rolled by, and carbon dioxide levels rose, forests used water more efficiently and this was true for all 21 sites.
This so-called fertilization effect has been independently confirmed in arid zones, again by indirect research, through the work of an Australian team studying satellite data, and also seems consistent with a finding reported in Nature Climate Change that tropical forest trees are now producing more flowers, even though the observed temperature rises in the tropics have so far only been modest.
The implication of the most recent research from the boreal and temperate forests is that plants could be partially closing their stomata to keep their carbon levels at a constant level. This finding, like much in science, raises as many questions as it answers. How plants “know” what to do in such circumstances, and how they do it, is still a mystery.
Plants exploit atmospheric carbon dioxide so it should be no surprise that a better supply leads to more efficient growth. But more carbon dioxide also means higher temperatures, more evaporation, more precipitation and more cloud cover—so it has been difficult to observe the impact.
Whether this will turn out in the long run to be a positive feedback that could, to some slight extent, slow global warming is uncertain.
Plants are also sensitive to extreme heat and drought, two other unwelcome companions of climate change due to human emissions of greenhouse gases such as carbon dioxide, so it is too soon to suggest that forests will emerge as the winners.
Other scientists still have to confirm the effect, and measure its scale more accurately. But the latest research does suggest trees are responding to change.
“Our analysis suggests that rising atmospheric carbon dioxide is having a direct and unexpectedly strong influence on ecosystem processes and biosphere-atmosphere interactions in temperate and boreal forests,” says one of the authors, Dave Hollinger of the U.S. Forest Service.
Visit EcoWatch’s CLIMATE CHANGE page for more related news on this topic.
Sweden's reindeer have a problem. In winter, they feed on lichens buried beneath the snow. But the climate crisis is making this difficult. Warmer temperatures mean moisture sometimes falls as rain instead of snow. When the air refreezes, a layer of ice forms between the reindeer and their meal, forcing them to wander further in search of ideal conditions. And sometimes, this means crossing busy roads.
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By Aaron W Hunter
A chance discovery of a beautifully preserved fossil in the desert landscape of Morocco has solved one of the great mysteries of biology and paleontology: how starfish evolved their arms.
The Pompeii of palaeontology. Aaron Hunter, Author provided<h2></h2><p>Although starfish might appear very robust animals, they are typically made up of lots of hard parts attached by ligaments and soft tissue which, upon death, quickly degrade. This means we rely on places like the Fezouata formations to provide snapshots of their evolution.</p><p>The starfish fossil record is patchy, especially at the critical time when many of these animal groups first appeared. Sorting out how each of the various types of ancient starfish relate to each other is like putting a puzzle together when many of the parts are missing.</p><h2>The Oldest Starfish</h2><p><em><a href="https://www.biorxiv.org/content/10.1101/216101v1.full.pdf" target="_blank" rel="noopener noreferrer">Cantabrigiaster</a></em> is the most primitive starfish-like animal to be discovered in the fossil record. It was discovered in 2003, but it has taken over 17 years to work out its true significance.</p><p>What makes <em>Cantabrigiaster</em> unique is that it lacks almost all the characteristics we find in brittle stars and starfish.</p><p>Starfish and brittle stars belong to the family Asterozoa. Their ancestors, the Somasteroids were especially fragile - before <em>Cantabrigiaster</em> we only had a handful of specimens. The celebrated Moroccan paleontologist Mohamed <a href="https://doi.org/10.1016/j.palaeo.2016.06.041" target="_blank" rel="noopener noreferrer">Ben Moula</a> and his local team was instrumental in discovering <a href="https://www.sciencedirect.com/science/article/abs/pii/S0031018216302334?via%3Dihub" target="_blank" rel="noopener noreferrer">these amazing fossils</a> near the town of Zagora, in Morocco.</p><h2>The Breakthrough</h2><p>Our breakthrough moment came when I compared the arms of <em>Cantabrigiaster</em> with those of modern sea lilles, filter feeders with long feathery arms that tend to be attached to the sea floor by a stem or stalk.</p><p>The striking similarity between these modern filter feeders and the ancient starfish led our team from the University of Cambridge and Harvard University to create a new analysis. We applied a biological model to the features of all the current early Asterozoa fossils in existence, along with a sample of their closest relatives.</p>
Cantabrigiaster is the most primitive starfish-like animal to be discovered in the fossil record. Aaron Hunter, Author provided<p>Our results demonstrate <em>Cantabrigiaster</em> is the most primitive of all the Asterozoa, and most likely evolved from ancient animals called crinoids that lived 250 million years before dinosaurs. The five arms of starfish are a relic left over from these ancestors. In the case of <em>Cantabrigiaster</em>, and its starfish descendants, it evolved by flipping upside-down so its arms are face down on the sediment to feed.</p><p>Although we sampled a relatively small numbers of those ancestors, one of the unexpected outcomes was it provided an idea of how they could be related to each other. Paleontologists studying echinoderms are often lost in detail as all the different groups are so radically different from each other, so it is hard to tell which evolved first.</p>
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