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South East Asia haze: What is slash-and-burn?

A patch of land being cleared by burning in Indonesia
Image caption There has been concern over the extent of land clearance for palm oil plantations in Indonesia

Singapore and parts of Malaysia and Indonesia have been shrouded in a dense, pungent smog in recent days caused by fires in Indonesia.

Pollution levels have hit record highs and while the blame game goes on, the one common factor has been the term "slash-and-burn".

What is slash-and-burn?

This is a technique used to clear patches of land - forest or peats - for plantation.

Under this practise, farmers cut down part of the vegetation on a patch of land and then set fire to the remainder. When started on peats, the fire is extremely difficult to control or stop.

These fires produce a thick smog and release a huge volume of greenhouse gases. The current haze is being caused by fires in Sumatra in Indonesia, much of which is a giant peat bog.

Indonesia's government has outlawed the use of fire to clear land.

Why do they use slash-and-burn?

Slash-and-burn is arguably the easiest way to clear the land.

According to some analysts, if a one hectare patch of land was to be cleared legally by chopping down the vegetation, it would produce nearly 500 tonnes of bio-mass.

It would take almost three years for that bio-mass to biodegrade and the land to become usable for plantations.

Using slash-and-burn makes the process much quicker and in most cases more cost effective, at least in the short run.

At the same time, burning also helps the farmers get rid of any disease that may have affected the crops in the vegetation.

Image caption The growing demand for palm oil has made the crop a lucrative farming option

What are they clearing the land for?

Some farmers are clearing the forest to plant crops. But the big concern is that many of these fires may have been started to burn rain forest so big corporations can plant oil palm plantations

Indonesia is the world's biggest producer of palm oil and the demand for the commodity has been rising. It is used in a range of products from biscuits, to shampoos, to cosmetics and bio fuels.

The surge in demand means that there is need for extra land for palm oil plantations.

So, how much land is being cleared for palm oil plantations?

Estimates vary greatly, but according to the World Wildlife Fund "it has been suggested that up to 300 football fields of forest are cleared every hour" across the globe to make way for palm oil plantations. That is more than 2 million hectares per year.

However, according to MR Chandran, advisor to the executive board of the Roundtable on Sustainable Palm Oil (RSPO), the figure is no more than 400,000 hectares per year.

Palm oil production is concentrated in Indonesia and Malaysia.

If slash-and-burn is illegal, why isn't it being stopped?

Some have pointed the finger at Indonesia authorities, saying that corruption and weak governance have contributed to the situation.

Greenpeace International said some companies in Indonesia appeared "to operate outside the law for years with little sanction".

It said the data on the current fires burning in Sumatra was incomplete, making it difficult to control the situation.

"The lack of government transparency makes it very hard for independent monitoring: concession maps are incomplete, data is lacking and we clearly have weak enforcement of laws," said Greenpeace South East Asia forest campaigner Yuyun Andrade.

In 1997-1998 a similar smog from Indonesia saw many countries in the region affected by haze. That led to an agreement on trans-boundary haze pollution being approved by the Association of Southeast Asian Nations (Asean) in 2002.

Indonesia is yet to ratify that agreement, which has only fuelled criticism over its handling of the issue.

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Media captionThe BBC's David Shukman explains the impact and cause of the haze

So who is responsible?

The nations affected have been trading comments. Singapore's government has called upon Indonesia to take adequate action.

Indonesia has named several firms, including Singapore and Malaysia-based palm oil companies, which it says may bear some responsibility for the fires.

Many of those companies have denied any involvement and have accused the local farmers of starting the fires to clear the land.

Asia Pacific Resources International Limited (APRIL) said that it has "completed a review of National Oceanic & Atmospheric Administration (NOAA) satellite imagery and have verified by direct field inspection that there are currently three fires in our concessions covering approximately 20 hectares".

"These fires have been contained and our fire fighters are working to extinguish them. APRIL confirmed that all fires it had detected originally started outside of its concession areas and had spread into its concessions."

Cargill said that it "has a strict no-burn policy and we can confirm that there are no hot spots or fires on our plantations in South Sumatra and West Kalimantan".

Malaysia's Sime Darby, one of the world's biggest palm oil companies, said it followed "a zero burning policy throughout its operations". Fires were reported in a concession area of one of its subsidiaries in Riau, it said, but it could not "exert control over activities beyond its operating areas and where it is occupied by others".

While the blame game goes on, the fires are still burning - which means the haze problems will continue.

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