6 March 2016, Climate News Network, Risk level rises for North American forests. The speed at which the climate is changing is outstripping forests’ ability to adapt to drier, hotter conditions across vast swathes of the US and Canada. Drought and climate change are now threatening almost all the forests of the continental US, according to new research. Scientists from 14 laboratories and institutions warn in the journal Global Change Biology that climate is changing faster than tree populations can adapt. Existing forests, effectively and literally rooted to the spot, are experiencing conditions hotter and less reliably rainy than those in which they had evolved. “Over the last two decades, warming temperatures and variable precipitation have increased the severity of forest droughts across much of the continental United States,” says James Clark, professor of global environmental change at Duke University, North Carolina. He and colleagues synthesised hundreds of studies to arrive at a snapshot of changing conditions and a prediction of troubles ahead. Ominous predictions Other research has already delivered ominous predictions for the forests of the US southwest, but the scientists warn that other, normally leafier parts of the continent face increasing stress. Dieback, bark beetle infestation and wildfire risk may no longer be confined to the western uplands. “While eastern forests have not experienced the types of changes seen in western forests in recent decades, they too are vulnerable to drought and could experience significant changes with increased severity, frequency, or duration in drought,” the authors say. Professor Clark puts it more bluntly: “Our analysis shows virtually all US forests are now experiencing change and are vulnerable to future declines. Given the uncertainty in our understanding of how forest species and stands adapt to rapid change, it’s going to be difficult to anticipate the type of forests that will be here in 20 to 40 years.” Read More here
Category Archives: Ecosystem Stress
3 March 2016, Science Daily, Greenland’s ice is getting darker, increasing risk of melting. Feedback loops from melting itself are driving changes in reflectivity. Greenland’s snowy surface has been getting darker over the past two decades, absorbing more heat from the sun and increasing snow melt, a new study of satellite data shows. That trend is likely to continue, with the surface’s reflectivity, or albedo, decreasing by as much as 10 percent by the end of the century, the study says. While soot blowing in from wildfires contributes to the problem, it hasn’t been driving the change, the study finds. The real culprits are two feedback loops created by the melting itself. One of those processes isn’t visible to the human eye, but it is having a profound effect. The results, published in the European Geosciences Union journal The Cryosphere, have global implications. Fresh meltwater pouring into the ocean from Greenland raises sea level and could affect ocean ecology and circulation. “You don’t necessarily have to have a ‘dirtier’ snowpack to make it dark,” said lead author Marco Tedesco, a research professor at Columbia University’s Lamont-Doherty Earth Observatory and adjunct scientist at NASA Goddard Institute of Space Studies. “A snowpack that might look ‘clean’ to our eyes can be more effective in absorbing solar radiation than a dirty one. Overall, what matters, it is the total amount of solar energy that the surface absorbs. This is the real driver of melting.” The feedback loops work like this: During a warm summer with clear skies and lots of solar radiation pouring in, the surface starts to melt. As the top layers of fresh snow disappear, old impurities, like dust from erosion or soot that blew in years before, begin to appear, darkening the surface. A warm summer can remove enough snow to allow several years of impurities to concentrate at the surface as surrounding snow layers disappear. At the same time, as the snow melts and refreezes, the grains of snow get larger. This is because the meltwater acts like glue, sticking grains together when the surface refreezes. The larger grains create a less reflective surface that allows more solar radiation to be absorbed. The impact of grain size on albedo — the ratio between reflected and incoming solar radiation — is strong in the infrared range, where humans can’t see, but satellite instruments can detect the change. Read More here
23 February 2016, The Conversation, Aboriginal fire management – part of the solution to destructive bushfires. As destructive bushfires become more common there is increasing political discussion how we manage them sustainably. Inevitably these debates raise questions of the past ecological effects of Aboriginal fire usage. There are two well-known narratives about Aboriginal fire use. One, popularised by Tim Flannery, stresses the ecologically disruptive impact of Aboriginal fire use. This storyline argues that the megafauna extinctions that immediately followed human colonisation in the ice age resulted in a ramping up of fire activity. This then led to the spread of flammable vegetation which now fuels bushfires. Another, promoted by Bill Gammage, suggests that the biodiverse landscapes that were colonised by the British were the direct product of skilful and sustained fire usage. Such broad-brush accounts give the impression that the specific details of Aboriginal fire usage are well-known and can be generalised across the entire continent. Sadly this is not the case. So rapid was the socio-ecological disruption of southern Australia that researchers have had to rely on historical sources, such as colonial texts and images, and tree rings, pollen and charcoal in lake sediments, to piece together how Aboriginal people burned the land. Such records are open to interpretation and there remains vigorous debate about the degree to which Aboriginal people shaped landscapes. Piecing together the past There are only a handful of detailed observational studies of the ecology of Aboriginal fire usage, and all from northern Australia, so there is dispute whether their findings can be extrapolated in the south. These studies demonstrate skilful use of fire that created fine-grained burn patterns, designed to promote food resources. For instance, a prime motive for burning savannas is attracting kangaroos to nutrient-rich grass that sprouts after the fire. In the desert, Aboriginal patch burning increases the habitat for sand goannas. In sum, there is mounting evidence that sustained Aboriginal fire use shaped many Australian landscapes by sharpening vegetation boundaries, maintaining open vegetation, and creating habitat for game species. Read More here
18 February 2016, The Conversation, Revealed: why some animals and plants will thrive under climate change. It’s mid-February and along Britain’s south coast gilt-head bream are drifting from the open sea into the estuaries. Meanwhile, thousands of little egrets are preparing to fly to continental Europe for breeding season, though a few hundred will remain in the UK. Across northern Europe, young wasp spiders will soon scamper out of their silky egg sacs. And this summer, countryside visitors throughout the south of England will catch sight of iridescent blue flashes as small red-eyed damselflies flit across ponds. These events all have one thing in common: they’re happening much further north than they would have as recently as 20 years ago. It’s not just a European thing. Polar bears are on the move, umbrella trees are creeping northwards through the US, and tropical birds in New Guinean mountains are retreating uphill. Southern Africa’s iconic quiver tree, which provides refridgeration in its hollowed out trunks, is itself escaping the heat and heading away from the equator. Across the world species are moving from their natural habitats. Fingers point at climate change. As areas become too hot or dry, many wildlife populations are declining. But on the flip side, some species are showing up in places that were historically too cold or wet. The story we usually hear is of terrible declines in plants and animals. The Pyrenean Frog is languishing on mountaintops on the Spanish-French border, for instance, unable to move to cooler climes. Magellanic penguin chicks are dying in storms brought on by climate change. Costa Rica’s golden toads, which are actually a rather amazing bright orange, are thought to have been driven to extinction by warmer, drier weather, among other factors. Read More here