Iconic authors help reveal record early flowering

"When I wrote the following pages, or rather the bulk of them, I lived alone, in the woods, a mile from any neighbor, in a house which I had built myself, on the shore of Walden Pond, in Concord, Massachusetts, and earned my living by the labor of my hands only." Those are the famous opening lines to Henry David Thoreau's Walden. Now, scientists have used Thoreau's notes on his surroundings to show how much earlier global warming has pushed plant flowering. Credit: Tim Hettler, via Flickr

“When I wrote the following pages, or rather the bulk of them, I lived alone, in the woods, a mile from any neighbor, in a house which I had built myself, on the shore of Walden Pond, in Concord, Massachusetts, and earned my living by the labor of my hands only.” Those are the famous opening lines to Henry David Thoreau’s Walden. Now, scientists have used Thoreau’s notes on his surroundings to show how much earlier global warming has pushed plant flowering. Credit: Tim Hettler, via Flickr

Notes from the last 150 years made by two environmental pioneers have helped show that the speed at which global warming is pushing spring events forward is not slowing. Boston University’s Libby Ellwood and her teammates compared flowering times recorded by Henry David Thoreau and Aldo Leopold to spring 2010 and 2012, the warmest and second warmest on record.  “Plants flowered earlier than ever before in these recent record warm years,” Libby told me. That advance is so closely linked to the warming our world’s experiencing, the researchers showed that they can predict flowering time from temperature. This knowledge could help predict climate change’s impact on crops.

“There will likely be winners and losers with climate change,” Libby said. “It is quite possible that some species will be able to use the warmer temperatures and longer growing season to their advantage. The risk for plants that begin growing as soon as the weather is warm though, is that the new spring growth and flowers are susceptible to late season frosts, and this can set back plant growth and reproduction.”

To understand what global warming is doing to other organisms, scientists have to find records about them from times when fossil fuel burning wasn’t as widespread as today. Thoreau and Leopold are best known as authors of books that lay the foundations of modern environmentalism. Both Thoreau’s Walden and Leopold’s A Sand County Almanac, published in 1854 and 1949 respectively, hold powerful ideas on the relationship between humans and nature. But both authors also studied phenology – the cycle of biological events such as plant flowering throughout the year. Read the rest of this entry »

Temperature cuts swathe through Australian seaweed

A mixed seaweed canopy in Western Australia, including Scytothalia dorycarpa (far right), which was completely killed along 100km of the Australian coast by a heatwave in 2011. Credit: Dan Smale

A mixed seaweed canopy in Western Australia, including Scytothalia dorycarpa (far right), which was completely killed along 100km of the Australian coast by a heatwave in 2011. Credit: Dan Smale

A record-breaking heat wave in 2011 killed a seaweed species that many fish and other creatures call home along a 100 km stretch of the Western Australian coast. That underlines the threat from climate change, which is driving more regular ‘extreme events’ like heatwaves, according to Dan Smale of the University of Western Australia (UWA). “Extreme events can wipe out species at their range edge incredibly quickly, which may have wide ranging implications for whole communities of associated plants and animals,” he said.

Metre-plus tall strands of Scytothalia dorycarpa seaweed sway around cool water rocky reefs in southern Australia, forming a playground for other species. It is thought to have evolved in cool conditions, and therefore to be sensitive to warmth. For that reason, in 2006, Dan and his UWA colleague Thomas Wernberg started tracking it in two main locations, Jurien Bay and Hamelin Bay, and 27 other sites. “We suggested that by monitoring its abundance and distribution, we could detect ecologically-significant climate change impacts over periods of years to decades,” Dan said. “We did not realise, however, that the highest-magnitude seawater warming event on record was just around the corner, and we did not expect to see such sudden and extensive shifts in its distribution.”

That extreme was reached in 2011 during the cooler ‘La Niña’ phase of the El Niño Southern Oscillation climate cycle. By contrast to the current Australian heatwave, temperatures rose thanks to an especially strong La Niña increasing the flow of warm water from the tropics. In March 2011 Thomas and Dan measured sea surface temperatures up to 4°C higher than the average for 2006-2010. The heatwave temperatures stayed more than 2°C above the 2006-2010 level for around 10 weeks in both bays. Read the rest of this entry »

Delays raise emission halt urgency

The inventors of the idea of using wedges to represent efforts that will grow to prevent a billion tonnes of CO2 emissions per year over 50 years made a game out of it. However, University of California, Irvine's Steve Davis underlines that  our ongoing failure to properly put the idea into action is very serious. Credit: Carbon Mitigation Initiative/Princeton University

The inventors of the idea of using wedges to represent efforts that will grow to prevent a billion tonnes of CO2 emissions per year over 50 years made a game out of it. However, University of California, Irvine’s Steve Davis underlines that our ongoing failure to properly put the idea into action is very serious. Credit: Carbon Mitigation Initiative/Princeton University

We need to work towards completely cutting greenhouse gas emissions from energy generation for the goal of keeping global warming below 2°C to be realistic. So says Steve Davis at University of California, Irvine, who has updated a powerful method to make it easier to see what emission cuts are needed. That method originally just worked towards stopping emissions increasing, but Davis says that’s not enough today. “If you’ve been gaining weight and want to lose it, you don’t set a goal of eating just enough sweets to hold your weight constant for a few years, you set a goal of no sweets and set about losing weight right away,” Steve told me. “Why shouldn’t the same thing be true for carbon emissions?”

It’s hard to imagine how we can slow and stop emissions. In 2004, that drove scientists Stephen Pacala and Robert Socolow at Princeton University in New Jersey to come up with the idea of breaking the cuts needed into wedges. Each wedge is a unit of effort in stopping CO2 production, starting from a small beginning and becoming a massive impact. Over 50 years, each wedge of effort grows steadily from zero to a billion tons, or gigaton, of carbon emissions avoided per year. We can use the idea to decide how to cut out each wedge, assigning them to particular reduction efforts and technologies. Since their invention, wedges have been used to teach and make decisions about fighting climate change.

In their original study, the Princeton scientists just used the wedges  to bring our emissions to a stable level. At the time they found this would stop levels of the greenhouse gas in the air going above 500 parts per million (ppm). Reducing emissions from that level to zero would then have put a limit on climate change. However, accelerating emissions since their study have changed the starting point. Read the rest of this entry »

Climate limits room at the global dinner table

Reducing tillage used to prepare soil in farming can help reduce carbon emissions without also reducing crop yields. Credit: USDA Natural Resources Conservation Service

Reducing tillage used to prepare soil in farming can help reduce carbon emissions without also reducing crop yields. Credit: USDA Natural Resources Conservation Service

Part two of two

Another mid-winter feast has passed since I published the first part of this round-up of research linking food and global warming, its memory still pleasantly fresh in my mind. I’d hate to have to sacrifice any of it in the future. But what if I were forced to change or shrink my menu? You might not have to make these choices today, but scientists are helping farming adapt to a changing climate. They’re facing up to a big challenge: trying to reduce emissions, while maintaining food supplies.

As well as being affected by climate change, farming also produces some of the greenhouse gases that cause it – between one-tenth and one-third of the world’s emissions. Agricultural consultant Rob Carlton and his colleagues therefore looked at four different crop farming methods in March last year to see which would emit least greenhouse gas if the whole UK adopted it. The best approach was to dig up less left over plant material than conventional farming currently does, keeping more carbon trapped in the soil. This approach importantly produced the same amount of crops as conventional methods. That’s necessary, because converting pasture to arable land to make up crop shortfalls seen with other methods releases large amounts of greenhouse gas. “The need for emissions reductions should be viewed against demands on agriculture, which are increasing as the population and consumption increases and farmers diversify into industrial and fuel crops,” Rob said. Read the rest of this entry »

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