LINDELL BEACH, B.C. — Farmers can directly affect global climate change by improving land management and farming practices, says an Australian study.
Duane Norris and Peter Andrews wrote in theInternational Journal of Waterthat soil holds twice as much carbon as the atmosphere and three times as much as vegetation.
However, carbon oxidizes and is released into the atmosphere when soil is cleared, burned, plowed or drained, adding to the cumulative effects of global warming. In addition, soil health and plant fertility are also lost.
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Andrews, a farmer in the Australian state of New South Wales, attempted to restore degraded farmland to a dynamic ecosystem by recoupling the carbon and water cycles in a management approach he called natural sequence farming (NSF).
Norris, with degrees in agricultural science and sustainable landscape management from the University of Sydney, co-ordinates the NSF movement in Australia.
“Climate depends on many things,” Norris said in an e-mail interview.
“On land, climate is dependent on the presence of permanent green cover of plants managing the soil hydrology, which in turn, via the process of photosynthesis and evapotranspiration, manages the short water cycle. This is what creates localized rain and affects local climate. Many modern farming practices plow, cultivate and leave soil uncovered, creating desertification. Rain does not fall often on deserts.”
Norris said these traditional farming methods have led to a serious decline in soil quality in Australia, with levels only one tenth what they were 200 years ago before European settlement.
Scientists estimate that soil once contained carbon matter that was 4,000 to 10,000 years old but now hold carbon that is only two years old.
This is because livestock have overgrazed the land and bared the soil, leaving it in an oxidizing state so that the stored carbon can dissipate into the atmosphere.
“Plants are required as the ‘engineers’ to manage both water and carbon dioxide (to build soil fertility),” said Norris.
Remove the plants and the whole cycle is disrupted. (It) causes water to dissipate, leaving a hotter landscape while CO2 is redistributed back to the atmosphere. (But) the (short water cycle) on a landscape manages temperature by moderating between extremes.”
Carbon content of the soil increases and growing conditions improve when vegetation, even weedy cover, is left and allowed to break down.
Plants also help cool the local atmosphere through the evaporation of moisture from leaves.
Moisture contributes to the formation of rain clouds, producing showers that contribute to the short water cycle in a local area.
Norris and Andrews said in their report that careful water management, planting, mulch farming, contour farming and alley farming, where crops are grown between widely spaced rows of trees or shrubs, all work together to remediate degraded land and conserve water.
Norris said the tools to build a sustainable farming system are within reach.
Whatever is in soil that makes it fertile has been put there by plants, the authors said.
The environment runs on energy and plants are the means of generating and accumulating that energy. They said the roles of water, plants and soil in maintaining a landscape are each part of a complex, historically evolved system of interlocking cycles that is controlled by plants.
“Any practice that aims to stop water, energy and matter from leaving the farming system is to be encouraged,” said Norris.
