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The shelter forest

New Zealand's proposed contribution to reduce atmospheric carbon, and help mitigate climate change, is to plant large numbers of monoculture trees, although planting forests conflicts with increasing food demands — or does it? asks Gisborne man Marcus Williams.

The shelter forest (SF) concept proposes trees can be planted in ways that increase land productivity, address climate change and provide additional benefits.

“The concept is we should plant trees as shelter forest belts across all land, including the most productive flat land,” says Mr Williams.

Under SF, 20 percent of all agricultural land would be planted in forest belts 15 metres or so in width. This would provide belts of forest rather than single lines of trees. Three rows of trees of mixed species could be inter-planted with three rows of selected understory plants that could be harvested on a rotational basis. This would mean the integrity of the shelter function is maintained.

Shelter planted at the aptly named Windwhistle in Canterbury was observed to result in a dramatic increase in productivity, says Mr Williams.

“That was largely due to breaking down the wind. Shelter is also required for most permanent crops. We know shelter has a significant economic value.”

Productivity gains from the shelter alone will more than compensate for the land taken out of production. Problems with livestock due to extreme cold and heat would also be mitigated by the shelter forest belts.

Carbon sequestration

“We understand carbon is a problem,” says Mr Williams.

“One-third of excess carbon in the atmosphere comes from topsoils around the world.”

Soil specialist, Professor John Crawford of Sydney University, says within 50 years agrarian countries will be able to produce only 70 percent of what is produced now. This drop in food production will be faced by population that demands 50 percent more in food production.

“One benefit of carbon in the soil is it becomes a water reservoir,” says Mr Williams. “It holds 20 times its own weight in water.”

Massey University scientists have measured soil carbon sequestration more than 40m from shelter-belts.

Part of the solution for the projected food deficit of 50 percent is the use of ramial chipped wood, says Mr Williams.

Ramial chipped wood is a type of woodchips made solely from small to medium-sized branches. These can be chipped on site to create biodegradable material that enhances soil fertility.

In the late 1970s, Laval University (Quebec) research into large piles of slash left after logging produced positive results. Strawberries in Quebec and tomatoes in Senegal produced yield increases of 300 percent and 1000 percent respectively.

“Chipped up ramial mixed with soil increases carbon in the soil; the carbon is locked in. It's like using a raw form of compost, except it's woodchip,” says Mr Williams.

The yields demonstrated by Laval University research point to extraordinary economic and environmental possibilities, he says.

SHELTER: Pruned to about seven metres, a kawa poplar shelter belt behind a deer fence is raised high enough to let sunlight through. This provides puddles of shadows rather than heavy shade which suppresses grass growth, says Gisborne man Marcus Williams.Picture supplied