Another negative climate feedback found, this time in grasslands

In grasslands, longer spring growing season offsets higher summer temperatures
North American grasslands face mixed bag of climate change effects

Kendall Grassland in southeastern Arizona is one of many sites in the research project. CREDIT R.L. Scott, USDA-ARS

Kendall Grassland in southeastern Arizona is one of many sites in the research project. CREDIT R.L. Scott, USDA-ARS

From the NATIONAL SCIENCE FOUNDATION

Grasslands across North America will face higher summer temperatures and widespread drought by the end of the century, according to a new study.

But those negative effects in vegetation growth will be largely offset, the research predicts, by an earlier start to the spring growing season and warmer winter temperatures.

Led by ecologists Andrew Richardson and Koen Hufkens of Harvard University, a team of researchers developed a detailed model that enables predictions of how grasslands from Canada to Mexico will react to climate change.

The model is described in a paper published today in the journal Nature Climate Change.

New insights into climate change effects on grasslands

“This research brings new insights into predicting future climate-driven changes in grasslands,” says Elizabeth Blood, program director in the National Science Foundation’s Division of Environmental Biology, which funded the research. “The results show that annual grassland cover and productivity will increase despite drought-induced reductions in summer productivity and cover.”

Ultimately the growing season gets split into two parts, Hufkens said. “You have an earlier spring flush of vegetation, followed by a summer depression where the vegetation withers, then at the end of the season, you see the vegetation rebound again.”

Adds Richardson, “The good news is that total grassland productivity is not going to decline, at least for most of the region. But the bad news is that we’re going to have this new seasonality that is outside of current practices for rangeland management — and how to adapt to that is unknown.”

To understand the effects of climate change on grasslands, the scientists created a model of the hydrology and vegetation of the region. They used data from the PhenoCam Network, a collection of some 250 Internet-connected cameras that capture images of local vegetation conditions every half-hour.

Using 14 sites that represent a variety of climates, the biologists ran the model against a metric of “greenness” to ensure that it could reproduce results in line with real-world observations.

“These were sites from across North America, from Canada to New Mexico and from California to Illinois,” Richardson said. “We used the greenness of the vegetation as a proxy for the activity of that vegetation. We were then able to run the model into the future.”

The region was divided into thousands of 10 square-kilometer blocks, allowing researchers to spot important differences in the response to climate change.

“That allows us to look at how patterns emerge in different areas,” Hufkens said.

Importantly, Richardson said, the model also uses a daily rather than monthly time step.

Changing seasonal patterns bring challenges

“Grasslands are different than forests in that they respond very quickly to moisture pulses,” said Richardson. “This model takes advantage of that — by running at a daily time scale, it can better represent changing patterns.”

The changing conditions could present challenges for farmers, ranchers and others who rely on predictable seasonal changes to manage the landscape.

“These shifting seasons will present new tests for management practices,” Richardson cautioned.

For grasslands, the increases in production and losses due to higher summer temperatures largely balance out, Hufkens said.

Although the results suggest that climate change may have some positive effects, both Hufkens and Richardson warned that they are the result of a delicate balance.

“It’s getting more arid and that’s causing more intense summer droughts, but because of a changing seasonality, vegetation growth is shifting,” said Richardson.

The negative effects of drought on ecosystem production can be offset, he believes. “But that raises new questions about appropriate management responses,” he said.

“Relying on this increase in productivity, or expecting that climate change will have long-term benefits because of results like this, is like playing the lottery — the odds are not very good.”

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43 thoughts on “Another negative climate feedback found, this time in grasslands

  1. “…a detailed model that enables predictions of how grasslands from Canada to Mexico will react to climate change.”

    A model. Which predicts how grasslands will react to climate change. So climate change (=rising temps?) is assumed. What does it predict if the Fallen Angels scenario emerges instead?

    • You hit it perfectly. The history of world climate (particularly for the last 10,000 years) shows that we have both warming and cooling on a periodic basis. Nearly all of the recent “studies” by alarmists in the last 30 years show only warming. The current very low activity of our sun matches closely to the early 1900’s or even the late 1950’s thru 1979 in which we had significant global cooling. In fact, some very knowledgeable scientists in Sweden, Russia, and the U.S. are now predicting an extended (40 year) period of cooling that will follow the current “pause.” If this really occurs, what do their models tell us???

  2. Gee. Didn’t Tremberth just predict wetter winters from climate change? Or was it just more snow? As the IPCC models cannot predict even temperature, how the bloody hell can they predict rain?

    • Haven’t the global warming shamans been telling us that the models are only valid for the whole earth.
      The regional forecasts are worthless.
      Unless of course you need to use them to scam another research grant.

    • [citation]
      “We know for certain, for instance, that for some reason, for some time in the beginning, there were ‘hot lumps’…
      “Animals… without backbones… hid from each other, or fell down…”
      “Hundreds of year later, during the late Devouring period, fish became obnoxious…”
      “Mosquitoes collided aimlessly in the dense gas…”

  3. The Boyz of NCAR Boulder heard about a grass study and got all giddy. Store shelves were promptly stripped of Doritos.

  4. Although the results suggest that climate change may have some positive effects, both Hufkens and Richardson warned that they are the result of a delicate balance.

    We really do live in a Goldilocks era.

  5. I just did a model that shows since we are using sooooo much fossil fuel, the earth is getting lighter and we are going to crash into the sun. If you say there is no mass loss you are a denier, co2 is lighter than oil!

  6. 14 sites, total of 250 cameras or less, extrapolated to a model of thousands of 10 sq km blocks from Canada to New Mexico, California to Illinois…sounds reasonable.

    • Way, way back in the early to mid-1800’s my clan moved relentlessly across the continent in wagons. When it was a fair deal colder than today. All towns named ‘Lima’ and ‘Peru’ were founded by the Pettit clan, for example (in honor of the founding father who was a pirate) exist across the northern plains states.

      They did this on foot with ox teams and horses! And thrived, not just survived. All the hysterics screaming at us that small shifts (to warmer!) are going to kill us is hilarious considering how I know for certain, my ancestors would have loved to have shorter winters!!!

      And farmers adjusting farming techniques and plants to take advantage of weather changes? They have been doing this for the last 8,000 years! They started doing this before writing was invented! Writing was invented because of agriculture needing records!!!!

      • Ah! But those of us who know who our ancestors WERE, and what they did (not to mention spending time outside) are at quite an advantage over the effete urbanites who’ve never had dirt under their fingernails, pile on the Patagonia to go from the elevator to the subway, and for whom “Nature” is abstract theory. Not to mention the increasing spwan of “baby-daddies,” sperm banks, petri dishes and surrogates who have no one to look to for ancestral advice but Big Media.

  7. Another thing I’ve never read anything about, and related to this, is what are instantaneous CO2 levels above vast swathes of grasslands at 280 and 400 ppm global atmospheric CO2 respectively (forests too and cornfields). I imagine the difference is probably not 120 ppm due to the rapid uptake which would, of course, not reduce the mean free path of a surface-derived photon as much as the models might say it does.

    Anyone seen any literature on this, or were the authors’ papers rejected and they were sent to reeducation camps ??

  8. So models tuned to…hours of sunlight, temperature, rainfall, humidity, etc…how about CO2? Pretty fixed since this project was started. So how can they confirm model results for higher levels of CO2 in the future?

  9. Yes, we could eventually get back to where we were in the 1930’s, the benchmark for heat and drought. But, so far it’s been going in the opposite direction. I live in South Dakota, and the summers have been getting cooler and wetter. Of course, this could change back the other way at any time. These trends are cyclical.

  10. Welll…

    1. More productive Spring growing seasons would be simply a beneficial effect of a warmer climate, not a “feedback,” except that more plant growth removes more CO2 from the air, reducing the CO2 forcing.

    2. Their “model” and ideology say that anthropogenic climate change will cause it to get “more arid” with “more intense summer droughts,” but there’s scant real world evidence of that.

    3. Extra CO2 not only makes plants grow faster, it also makes plants more drought resistant and water-efficient, by improving stomatal conductance relative to transpiration, which is especially helpful in arid regions. As a result, some of the world’s deserts and near-deserts are greening:
    http://news.nationalgeographic.com/news/2009/07/090731-green-sahara.html

    When air passes through plant stomata (pores), two things happen: the plant absorbs CO2, and the plant loses water through transpiration. When CO2 levels are higher, the ratio of CO2 absorbed to water lost improves, which improves both plant growth and drought resistance. The plants also commonly respond to elevated CO2 by reducing the density of the stomata in their leaves, which reduces water loss. Google finds many articles:
    https://www.google.com/search?q=co2+and+(“drought+resistance”+OR+”drought+tolerance”+OR+”drought+stress”)

  11. Ocean evaporation, the main global source, increases with temperature. Precipitation in the long run equals evaporation. So why do the models show more drought with warming?

    • Richord Petschauer — it is otherway round. Drought increases warmness. Drought condition means cloud free condition on many days. Wet condition means clouds on many days. In India 2002 and 2009 drought years the temperature has gone up by 0.7 & 0.9 oC.

      Dr. S. Jeevananda Reddy

  12. So much BS, so little time. C’mon, grasses are C4, not the explosive, the current culmination of the evolution of photosynthesis. They can get by on less water and less CO2 because they get what they need keeping their stomata open less.

    Very likely they evolved in response to the steady decline in the trifecta of temperature, humidity, and CO2 since the Paleocene.

    If you are worried because they sequester less CO2, you are right. Will an earlier spring increase their photosynthesis? Shure.

    Land use change is significant, but human influence is no more than an extension of a process that began 55 million years ago. Extra CO2 reverses the “field” on the grasses (including corn and sugarcane). Their adaptation becomes less important, and the C3 plants will twist and shout.

    • Actually, grassland is one of the biggest CO2 sinks that there is.

      Each acre of grassland sinks 0.3 tons of Carbon each and every year into the soil. (This has been carefully measured in dozens and dozens of studies).

      If you run the numbers on how much grassland and savannah there is on the planet, grass is probably sinking between 1 to 2 billion tons of Carbon each year, 25% to 50% of the total net absorption of CO2 – it rivals the ocean sink in fact.

      C4 grasses evolved between 32 to 24 million years ago. As soon as they became wide-spread and populated areas which were previously desert (areas which were hot and had lower rainfall), CO2 levels promptly fell to 280 ppm, for probably the very first time in Earth history. C4 grasses allowed for a greater CO2 sink from vegetation because it could grow in areas where other plants couldn’t grow, hot and dry places or even areas like the forest floor. The vegetation biome increased as a result and the CO2 sink provided by vegetation increased.

      A picture is worth a thousand words. Grass, black Carbon builds up quickly, good soil, CO2 sink.

      • Ok, but the hot, dry areas also expanded throughout the Paleogene. Their concern is that we are abetting this process by trading acres of rainforest for acres of grass.

    • Most C4 plants are grasses but it is not true that most grasses are C4.
      Wheat, barley, oats, rice, rye, fescue and Kentucky bluegrass are C3. Corn is C4.

      • Thanks, I knew that some were C3, but not that impressive roster. Do you happen to know what the percentage of C3 grasses is in a typical savannah?

  13. The opening statement is incomplete as I show here:

    Grasslands across North America will face higher summer temperatures and widespread drought by the end of the century, according to a new study

    . To be meaningful the missing part needs to be filled in. It begins with “if the following is true:”. What ever the following might be is the complete justification for the first sentence. The conversation cannot continue until that is provided. I’ll wait…

  14. When the first images came from satellite OCO2 , with much, and justified, fanfare. one of them was of solar induced chlorophyll fluorescence . Presumably this will give a near global view of “greenness” as required by researchers such as those responsible for this study.
    However since that first announcement I have seen very little about the CO2 concentrations and nothing about the chlorophyll fluorescent intensities. Have I simply not been assiduous enough in my research or have NASA /JPL not bothered to follow up their, surely quite expensive , project.

  15. With the amount of snow in the West, this winter, I would put the predicted drought next year. Lots of moisture this year, thanks to El Nino. ;-)

  16. Having spent my entire life on the prairies I enjoyed reading this study. Most of what is said has happened over my 73 years of working and playing on the land. The reaction to change postulated, therefore, makes sense. They do insinuate that the grasslands are fragile, a point I would argue. Actually, the prairies are tough as hell. I’ve seen them survive extreme drought and bounce back quickly with moisture. I have seen them inundated with overland flooding and regenerate quickly after the land drains. Life has tremendous tenacity and the earth heals quickly after either natural or anthropogenic disturbance. Only major urban areas have been destroyed.

    The authors seemingly had to question how farmers/ranchers can adjust practices to accommodate change. This line of thought may appeal to city folks, but those who live on the land will have no problem keeping the land productive if the slow changes do occur in the directions suggested. Most academics and theoretical government scientists have no clue how much farming has adjusted since the dust bowl. The combination of land practices, mechanization and plant genetics is what dumped Ehrlich’s Malthusian scare of the 60’s into the garbage bin.

  17. They could have conducted this entire study by evaluating how often lawns get mowed in the suburbs of Pittsburgh between April and October.

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