Downturn in plant production suggests drying world
By Erika Fredickson
As a gardener, it’s easy to assume that the only drawback to an extended growing season is that you’ll wind up with an excess of zucchini. On a global scale, climate change has led to longer growing seasons in higher latitudes with some positive agricultural benefits.
In 2007 for instance, The New York Times reported that Greenland – which mostly produces potatoes and livestock and imports everything else – had started growing and selling local cauliflower, broccoli and cabbage for the first time. Places such as Montana also are predicted to see a pattern of longer growing seasons over time, with spring arriving early the past few years.
In 2003 UM climate scientists Ramakrishna Nemani (now a NASA senior scientist) and Steve Running published a study showing that the net primary production (NPP), which is the amount of atmospheric carbon fixed by plants and accumulated by biomass, had increased by 6 percent between 1982 and 1999. In other words, it seemed all that global warming was making the planet greener.
“That was picked up in the media as good news,” Running says. “It was a fairly common presumption that, of all the different climate change impacts under way, increasing primary production was one that seemed pretty stable.”
Since that publication, however, the trajectory has changed. In a routine analysis of their data from a satellite that was launched in December 1999, UM scientist Maosheng Zhao and Running discovered that although growing seasons continue to get longer in high-latitude boreal regions, tropical and subtropical areas are seeing more drought. Because the issue of climate change is so politically charged and policy-sensitive, Zhao and Running updated the findings in a new study published in August in the prestigious journal Science showing that NPP has decreased because of drought between 2000 and 2009. That means, overall, the planet is not getting greener.
“Warming-associated heat and drought might become more frequent in the future as more carbon is emitted into the atmosphere,” Zhao says. “Thus, drought-induced reduction in NPP in the past decade may provide us an early warning on negative effects of future climate change on ecosystems and human society.”
Running says, “The other side of the coin is that when a long growing season runs out of water – just like your garden – then your growth trajectory goes down. And that clearly was the case this past decade.”
Regions such as Australia and South America have been hit hardest. During the past decade, there were reports of increasing severity and frequency of drought resulting in pastures turning to dust bowls and fresh rivers becoming sluggish brown streams. The decrease in plant productivity in these areas has had a negative pull on NPP, an overall 1 percent decrease.
Sound miniscule? It’s not.
“It’s not a lot compared to zero,” Running says. “But it is a lot compared to the positive 6 percent rise that our previous paper had. To us, the difference isn’t from zero to negative 1. It’s from positive 6 to negative 1, and that’s a much bigger change in trajectory.”
It’s not easy to project what the decrease in NPP means for people. Running makes it clear that this study doesn’t predict the future – it only shows what’s been happening in the recent past.
“There’s no direct presumption that this trend will continue on a global scale,” he says. “We don’t know what the pace of increasing will be exactly, and we certainly don’t know what rainfall will be.”
In fact, the energy balance – incoming energy, solar radiation, partitioning and outgoing energy – is more easily measured and understood. Hyrdrologic components –cloud formation, thunderstorm development and rainfall gradients on mountainsides – are not. Models created by scientists predicting temperature, therefore, tend to be similar. Models predicting precipitation range from “wet” to “dry” to everything in between.
“It really shows you there isn’t consensus in the climate model community on how to do the hydrologic cycle,” Running says. “There aren’t sufficient direct measurements to be able to clearly get the physics right.”
Though climate change impacts are difficult to predict for the future, current on-the-ground impacts can be seen in a fairly exact manner. Running’s lab wrote the software that processes global analysis data for NASA, and scientists there have kept their eyes on the data for more than 20 years. Every year they calculate plant production of every square kilometer on Earth, which is added up every eight days all year long. Each year the science team also calculates the anomaly for that year – below- and above-average numbers – relative to all other years in the data set for each pixel.
“You evaluate that pixel and think of it simply as: Did that pixel have a good year or a bad year?” Running says. “The nice thing about that is it’s very easy to see. And when you see a whole area that all had a bad year, it really jumps out at you. An anomaly for one year you can write off as simple weather variability. It only gets climatologically interesting and policy-relevant in carbon cycle science when you start seeing a big region going year after year after year in [one direction].”
The truth is, Running says, we can’t logically expect the biosphere to provide constantly increasing levels of one kind of ecosystem service, such as longer growing seasons, without throwing off balance in other ways that might lead to heavy drought and other disasters. When areas start having multiple bad years, the result often adds up on the ground in crop failures, wildfires and other ecosystem problems. And if these droughts continue, says Running, food security could be an issue.
“What I’m particularly concerned about is the enthusiasm for bio-energy where it could really become a direct competitor for food production in a way that corn ethanol did for a short while a few years back,” he says. “I think that was just a warm-up to what could happen in the future on a major scale.”
By Erika Fredrickson
In fall 2009 UM launched a climate change studies minor for undergraduates, the first of its kind in the nation. The interdisciplinary program allows students from many different departments across campus to take classes in climate change and apply that knowledge within the context of their elected major.
The 40 students currently registered for the minor come from departments such as environmental studies and geosciences, but also from programs less traditionally focused on climate change like business, philosophy and journalism. All registered students take course work in three areas: climate science, society and solutions. The science classes provide background in climatology; the society aspect includes courses in ethics, policy and communications; and solutions gives students the opportunity to problem solve through community and campuswide projects or internships, technology and policymaking.
“We started developing this degree because we knew this was an important issue,” says Nicky Phear, program coordinator and instructor for the climate change minor. “We were surprised to find that there aren’t any other programs, or at least not that we could find, that offered students a program in climate change at the undergraduate level.”
Phear says climate change issues have bubbled up across campus for years, but the drive to make it a minor was encouraged by Royce Engstrom, the UM provost who has since become the University’s 17th president. The curriculum was approved in spring 2009 and put into effect the following semester.
“Students were already taking courses in advance of it being approved,” Phear says, “so we were actually able to graduate three students last spring with the minor. I think it’s kind of a tribute to our University and our capacity to build relations and have strong relations across departments, colleges and schools that we can make this happen.”
Students pursuing climate change minors already have begun to make their mark on campus and beyond. Several have worked on campus sustainability projects, including serving as eco-reps to help encourage other students to make changes in behavior – from riding their bikes to cutting down energy use in residence halls. Students also have completed greenhouse gas inventories for local businesses, while others have invested in national policy campaigns and worked on mitigating climate impacts on fisheries.
During Wintersession, students pursuing the minor traveled to Vietnam to learn about climate change effects on local livelihoods and some adaptation strategies in the context of the country’s society, environment and economy. Additionally, during a summer field course called Cycle the Rockies, students bike across the state from Billings to Glacier National Park and, on the way, talk with community members building renewable energy, ranchers dealing with drought and scientists studying melting glaciers.
“This issue of climate change is hard to grasp because both the impacts and solutions are so big-scale in terms of our understanding right now,” Phear says. “Any way we can bring it closer to home is really helpful for understanding.”
“It’s clear to me that for humanity to wiggle out of this mess, we’ll have to rebuild society over the next century,” he says. “This minor turns out to be very innovative. I think that is ultimately what solving this issue will require.”
Photo caption: UM’s Nicky Phear coordinates the nation’s first climate change minor program.
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