Sustainable farming curbs greenhouses gases


Our final climate offering of the day blends two of our favorite topics, climate change and sustainable agriculture,m with a special focus on biochar [also known as terra preta]

The pre-Columbian inhabitants of the Amazon Basin had a remarkable secret, lost after their advanced civilization was destroyed by the disease brought by European explorers.

Sailing up the previously unexplored rive, Spanish explorer Francisco de Orellana, traveled down the Amazon in December 1541 on a journey that would last eight months before he sailed into Pacific Ocean, along the way discovering a rich, densely settled civilization producing high crop yields in the rain forest where, contrary to popular perceptions, soils are typically thin and poor.

Orellana’s stories helped fuel the myth of El Dorado, the famous lost City of Gold, but when later explorer’s sailed the Amazon, they found no flourishing cities, leaving Orellana in dispute for the next 500 years until archaeologists found proof of his claims in buried cities and soil rich in pot sherds and bit of partially combusted wood, or char.

The combination of charcoal and pottery turned thin, dreploeted soils in ricb black earth [in Spanish, terra preta], capable of yielding an agricultural bounty able to support a dense, prosperous population.

From David Bennett of the Delta Farm Press:

The properties of terra preta are amazing. Even thousands of years after creation, the soil remains fertile without need for any added fertilizer. For those living in Amazonia, terra preta is increasingly sought out as a commodity. Truckloads of the dark earth are often carted off and sold like potting soil.

Chock-full of charcoal, the soil is often several meters deep. It holds nutrients extremely well and seems to contain a microbial mix especially suited to agriculture.

And it was all created by a people the explorers called savages.

And if your interested in learning more the miraculous Native American discovery, here‘s a good place to start.

And now, on to to the latest development.

Study reveals natural solutions to combat climate change

From Cornell University:

Annual greenhouse gas emissions from all U.S. vehicles could be absorbed by forests, wetlands and agricultural lands – erasing a fifth of all greenhouse gas pollution, according to new research exploring natural climate solutions for the United States.

Peter Woodbury, senior research associate in the College of Agriculture and Life Sciences, is a co-author on research published Nov. 14 in Science Advances [open access].

The researchers analyzed 21 natural ways to mitigate climate change. They found that adjusting those natural management practices to increase carbon storage and avoid greenhouse emissions could equal 21 percent of the nation’s current net annual emissions. Increased reforestation could be equivalent to eliminating the emissions of 66 million passenger cars, according to the findings.

Improved management of existing croplands has an important role to play, according to the researchers. Woodbury, who led the cropland nutrient management portion of the study, and his colleagues found that many agricultural practices can significantly reduce greenhouse gas emissions.

Widespread adoption of cover crops – plants grown on farm fields when they would normally be left bare – aids in carbon sequestration and improves soil health, crop yields and yield consistency. The researchers also pointed to improved nutrient management practices that apply fertilizer when and where the crop needs it, using precision agriculture techniques.

These improved practices could reduce nitrogen use 22 percent, leading to a 33 percent reduction in field emissions and 29 percent reduction in upstream emissions with additional benefits for soil, air and water quality. In many cases, these practices also improve profitability for farmers.

“We have demonstrated that agriculture and forestry have real potential to both avoid greenhouse gas emissions and also remove carbon dioxide from the atmosphere and store it in plants and soil. At the same time, these practices have many other benefits such as improving soil health and water quality by reducing nutrient pollution of fresh water and the coastal zone,” said Woodbury, who develops models to quantify the sustainability of agricultural and forest ecosystems. Woodbury is a fellow at the Atkinson Center for a Sustainable Future.

The researchers pointed to biochar as one method with high potential, although further research is needed to overcome cultural, technological and cost barriers. In May, Cornell opened the largest pyrolysis kiln of its kind at a U.S. university to study the uses of biochar, a solid, charcoal-like material formed by heating biomass in the absence of oxygen. Biochar can help soil retain water and nutrients, as well as promote drainage when conditions are wet.

The researchers say that, along with reducing the impact of global warming, natural climate solutions have the potential to improve air and water quality, flood control, soil health and wildlife habitats.

Other solutions include: allowing longer periods between timber harvest to increase carbon storage; increasing controlled burns and strategic thinning in forests to reduce the risk of tree-killing fires; and reducing urban sprawl to preserve forests.

“These 21 natural climate solutions are really important because they can greatly reduce greenhouse gas emissions in the U.S. and the world while also providing other benefits including clean water, clean air and biodiversity,” said Woodbury.

BBC documents Orellana’s Amazon discoveries

Here’s a remarkable BBC documentary reporting on what scientists are finding as they retrace Orellana’s footsteps, with a special emphasis on terra preta.

The Secret of El Dorado

From the program notes:

The search for clues in the Amazon takes place at grass roots level – in the soil itself. Along Brazil’s Tapajos River, archaeologist Bill Woods has mapped numerous prehistoric sites, some with exquisite, 2,000 year old pottery. There is a common thread: the earth where people have lived is much darker than the rainforest soil nearby. Closer investigation showed that the two soils are the same, the dark loam is just a result of adding biological matter. The Brazilians call this fertile ground terra preta. It is renowned for its productivity and even sold by local people.

Archaeologists have surveyed the distribution of terra preta and found it correlates favourably with the places Orellana reported back in the 16th century. The land area is immense – twice the size of the UK. It seems the prehistoric Amazonian peoples transformed the earth beneath their feet. The terra preta could have sustained permanent intensive agriculture, which in turn would have fostered the development of advanced societies. Archaeologists like Bill Petersen, from the University of Vermont, now regard Orellana’s account as highly plausible. But if the first Conquistadors told the truth, what became of the people they described?

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