Written by Community Solutions Fellow, Peter Bane
Soil and water cycles have been systematically overlooked by climate scientists seeking the causal mechanism for global heating. Though climbing carbon and methane in the atmosphere undoubtedly contribute to heating the planet, their rising levels appear to be more a symptom than a cause—resulting from enormous human-made changes to soils and vegetation that have disrupted the small water cycle or evapotranspiration of water from land to sky. Vegetation in the form of forests, grasslands, and wetlands has regulated the climate through many swings of CO2 levels. However, the cumulative impact of 10,000 years of forest removal, agricultural degradation of soils, draining of wetlands, and urbanization—accelerating exponentially over the past three centuries—has so damaged the biosphere’s capacity to exhaust heat that we are rapidly approaching a threshold beyond which it may not be possible to reverse the process.
The science underpinning this thesis is not radical, being familiar to all school students—plants transpire large volumes of moisture, the latent heat of vaporization is immense, and these effects reach into the upper atmosphere—but its implications have been hidden in plain sight for some decades, in part because climate scientists have assumed that measuring the effects of these diffuse actions would be too difficult. Moreover, increasing activity in the large water cycle—which moves moisture from the oceans onto land and has become so very destructive with larger and larger storms—is probably masking declines in evapotranspiration over land. What is being realized today is that the level of moisture in the atmosphere is not constant, and may be as much as ten times the volume of water to be found in all Earth’s rivers. Nor is the outflow from continents to the sea a constant, but has steadily increased as forests are cleared, soil humus is oxidized, and pavement expands. The net outflow of water from the continents, exclusive of glacial outwash, may account for as much as 40% of sea level rise in the past half-century, an increase that has reached about 2-3 mm/year today. This is compounding problems not only of coastal flooding but of aridification across the globe.
The required response to this information, which radically shifts the paradigm around climate, is similar to what some have suggested heretofore, that carbon sinks must be increased even as carbon sources are reduced. The Rodale Institute has recently published research indicating that global changes to agriculture could sequester more carbon than is now entering the atmosphere from all human sources—and their solutions are neither the only nor the most powerful available.
However, reducing atmospheric carbon will be insufficient by itself to alter global heating in the near term (5-15 years), which is where our actions must be focused. Climate change is rapidly approaching a non-linear state due to positive feedback mechanisms.
Carbon sequestration in the form of soil repair and revegetation will be required to restore the small water cycle over land, but if sequestration becomes the goal without regard for hydrology, those efforts may be insufficient to alter the trajectory of global warming. We need our actions to have multiple effects. What this means is that carbon must be captured by plants and soils rather than from smokestacks as now proposed by technological ideologues. If we can repair the damage we have wreaked on biotic communities, the beneficial effects on the water cycle may achieve what we must try at all costs to do: prevent further heating and reverse the trend of recent decades.
The Arthur Morgan Institute for Community Solutions will be examining and publicizing research and case studies of carbon sequestration and water cycle restoration through blogs, a 2017 conference in collaboration with Bio4Climate, and an upcoming book upon which I am presently at work.