Dealing with a Dryer World

November 4, 2013


New study looks at climate change’s impact on the tiniest of critters, on whom the rest of us depend much more than we know.

Climate Central:

Manuel Delgado-Baquerizo of the Universidad Pablo de Olavide, in Seville, Spain, and fellow scientists report in Nature that they looked at soil samples from 224 dryland ecosystem plots in every continent except Antarctica.

Drylands matter: they account for more than 40 percent of the planet’s land surface and they support more than 38 percent of its population. Drylands add up, in the dusty language of science, to the largest “terrestrial biome” of all.

And even though on average more warmth will mean more evaporation, and therefore more water vapor in the atmosphere and more precipitation in some of those zones that already have ample rainfall, the pattern could be different in the arid lands.

All the calculations so far indicate that these drylands will increase in area, and become drier with time. Already 250 million people are trying to scrape an increasingly meager living from lands which are degrading swiftly, either because they are turning to desert, or because they are overgrazed.

Hard on microbes

But to make things worse, climate scientists predict that between 2080 and 2099, soil moisture will decrease by between 5 percent and 15 percent worldwide. And that in turn could have a profound effect on the levels of carbon and nitrogen nutrients naturally in the top soils.

What keeps soils alive, and productive, is the compost or humus of leaf litter, animal dung, withered roots and other decaying vegetation in the first meter or so of topsoil: this in turn feeds an invisible army of tiny creatures that recycle the nutrient elements for the next generation of plant life.

But these microbes also need water to thrive. The consortium of researchers predicted that as the soils got drier, biological activity would decrease, but geochemical processes would accelerate. That is, nutrients that depended on little living things in the soil would drain away, but other elements – phosphorus among them – would increase, because they would be winnowed from the rock by mechanical weathering or erosion.

The drop in nitrogen and carbon concentrations that occurs as soils become dryer could have serious effects on ecosystem services such as food production, carbon storage and biodiversity, according to the Nature paper published today.

Loss of nitrogen and carbon, which are the basic building blocks of living organisms, drastically affects land’s productivity, says Fernando T. Maestre, a biologist and geologist from King Juan Carlos University, Spain, and a co-author of the report.

“If plant productivity is reduced, the capability of the land to support livestock and crops will be affected and this will have a big impact on people who depend on them,” he tells SciDev.Net.

Drylands make up more than 40 per cent of the world’s land area, and host a similar proportion of the world’s population. Many are expected to get drier because of climate change.

The study measured the nitrogen, carbon and phosphorus content of soil at 224 sites across all continents except Antarctica, which together represent a wide range of soil and vegetation types, climates and species diversity.

As ecosystems became more arid, it found, both nitrogen and carbon concentrations decreased, which may significantly impair plant and microbial activity, with knock-on effects on organic decomposition and plant growth.

The study’s data suggest that “as global climate change progresses, the ecosystem properties of many drylands could pass a tipping point that will be difficult or impossible to reverse,” writes David A. Wardle, a researcher at the Swedish University of Agricultural Sciences, in an accompanying comment piece in Nature.


8 Responses to “Dealing with a Dryer World”

  1. kingdube Says:

    Microbes emit more than 10X the amount of CO2 to the atmosphere than do humans!

    • redskylite Says:

      True – natural sources do emit more than mankind, in 2012 it is estimated that man emitted a record 34.5 gigatonnes that is between 6x and 7x the emissions from nature. But nature is set up to process a certain amount of CO2, unfortunately man is upsetting the balance (by industry and deforestation), that is why NOAA showed CO2 climbing to 400 ppm in Hawaii last May (and slightly earlier in April 2012 in Barrow Alaska, and slightly less in the Southern Hemisphere, Cape Grim, Tasmania where it is expected to reach 400ppm in 2016. )

      Again we are totally ignoring the effects of methane, but what is your point ?, do you propose we start killing termites and microbes, to rebalance.

    • Irrelevant. Natural emissions of carbon dioxide are balanced by natural absorptions of carbon dioxide. You’ve left the Cycle out of the Carbon Cycle.

    • greenman3610 Says:

      to avoid these embarrassments,
      you have to do the viewing to get up to steam

    • andrewfez Says:

      The crocks are devolving.

      Dube, shouldn’t you at least be up to the ‘Foster/Rahmstorf 2011 is wrong because they forgot to add in the 60 year cycle tied to some crazy junk I’m forgetting because it’s not real’ crock?

      Maybe have one more go at the impending ice age?

  2. Jean Mcmahon Says:

    Industrial agriculturalist and all the Universities that brainwash people that it is ok to kill the soil should be in jail

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