The slash-and-burn method: useful or not for agriculture and biodiversity improvement??

Ancient farming method may help conserve savannahs

A fire-free farming method practiced by early inhabitants of the Amazonian savannahs could help inform efforts to conserve and rehabilitate these important ecosystems around the world, a study has found.

The research provides greater historic context for findings presented at a conference earlier this year (26 January), which suggested that slash-and-burn — in which trees are felled, left to dry and then burned to prepare land for farming — provides better growing conditions for valuable trees such as mahogany.
This latest study, published in Proceedings of the National Academy of Sciences (9 April), found that 800 years ago, prior to European settlement of Latin America, indigenous farmers had developed a technique known as 'raised-field' farming to manage land sustainably without using fire.

The method involved constructing small agricultural 'mounds' which promoted drainage, soil aeration and moisture retention. It conserved soil nutrients and organic matter, and preserved soil structure. 

The ancient technique was studied by researchers, who have created the first detailed picture of land use by documenting the very low frequencies of charcoal particles — an indicator of fire — in the savannahs of French Guyana. 

(Source: Aleida Rueda, 2012, http://www.enn.com/top_stories/article/44318)

And: 

Slash-and-burn 'improves tropical forest biodiversity'

[MEXICO CITY] Slash-and-burn agricultural practices, banned by governments because of the risk of uncontrolled fires, provide better growing conditions for valuable new trees than more modern methods of forest clearance, a study suggests.

Starting in 1996, researchers cleared 24 half-hectare areas of tropical forest in Quintana Roo state, in southern Mexico, using three methods: clear-felling, where most of the trees are cut down; bulldozing; and slash-and-burn, a practice common among smallholders, in which trees are felled, left to dry and then burned, to prepare the land for agriculture.

Mahogany seeds and seedlings were then planted and, after 11 years, the researchers compared the sites and found that slash-and-burn techniques had provided the best growing conditions for mahogany.
But, more interestingly, many valuable species had thrived in the slash-and-burn plots, said Laura Snook, one of the study authors and programme director at Bioversity International, which conducts research into agricultural biodiversity for the improvement of livelihoods.

In clear-felled areas, more than half of each area contained tree species of no commercial value, Snook said. In areas cleared by slash-and-burn, 60 per cent of species were commercially valuable. Additionally, the largest trees in slash-and-burn areas were 10 per cent bigger than those in bulldozed areas.

Snook was presenting the results of the study — which ended last year — at the annual conference of the International Society of Tropical Foresters, at Yale University, United States, last month (26 January). 

(Source: Aleida Rueda, 2012, http://www.enn.com/top_stories/article/43972)

Discussion:


Is the slash-and-burn (uncontrolled fires) really more valuable for biodiversity improvement than controlled fire method?