On trees and floods

26 02 2012

As everyone know by now, the king has, in the words of the Bangkok Post, “expressed his concern about deforestation and the resultant flooding in Thailand and has urged the government to take severe action against those responsible.”

2011 flood

He stated that there was a “need for the government to plant more trees and to take harsh punitive steps against ‘greedy’ civil servants who allowed illegal deforestation to occur. These approaches would help to both preserve forests and prevent flooding…”. The king blamed last year’s floods “on deforestation.” For deforestation, he said the “blame lies with some civil servants who are greedy and crave money,” and he urged the government to “protect the forests and severely punish those involved in deforestation…”.

Of course, the government an officialdom quickly praised the king and promised to implement his advice. Just to ensure the message is clear, the Post states “His Majesty the King is widely recognised as an expert in water and flood management.”

PPT likes trees and forests and believes that planting trees is a valuable activity for all kinds of reasons. However, the idea that forest depletion was the cause of 2011’s catastrophic floods would seem to be questionable given the high floods of several decades and centuries past, when there was plenty of forest cover. That this is all about “greedy” officials is also questionable. What about greedy capitalists? What about road-building and military anti-communist insurgency? What about the promotion of big dams, large-scale irrigation, eucalyptus plantations, and so on?

But these are non-specialist observations and simplistic accounts ignore some extensive scientific debates about forests and floods? Perhaps the most immediate “lesson” is that this topic is highly controversial and deeply embroiled in discussions of theory and statistics (for the statistically minded, see here). The basic point from the real experts seems to be that simplistic associations of floods – especially 50-100 year deluges – and forests need careful reconsideration.

The FAO had a report in 2005 that summarized scientific data (the PDF is here) and was itself controversial. The FAO stated:

Much has been written about floods, their causes and impacts. Debate has been intense about how to prevent, mitigate and manage them. Each tragic event inevitably becomes a political issue. Political survival demands that politicians are seen as responding to each crisis in quick fashion. Thus, officials seek immediate answers and short-term solutions. In many countries, there is widespread belief – including among many foresters – that forests can prevent or reduce floods. Therefore, an immediate, frequently drawn conclusion is that floods occur because forests have been cleared or degraded. Hence it is but a small step to presume that the continuing deforestation of Asia’s watersheds is the cause of the misery brought to millions of people every year.

The reality, however, is that direct links between deforestation and floods are far from certain. Although the media attributes virtually every flood-related tragedy to human activities – particularly to agricultural expansion and timber harvesting (typically characterised by the press as ‘rampant illegal logging’ irrespective of legality or harvesting methods employed) – hydrological systems are so complex that it is extremely difficult to disentangle the impacts of land use from those of natural processes and phenomena.

In the case of upland/lowland as well as forest and flood relationships, existing ‘knowledge’ is frequently based more on perceived wisdom, or myths, than on science. In the rush to identify the culprits for the most recent disasters, assumptions are made about processes in one region based on observations from other regions which often have quite different environmental characteristics, or by extrapolating from small to large scales.

Oversimplification is common, frequently leading to initiatives such as logging bans or the resettlement of people residing in watershed areas – often with minimal environmental benefits but very definite negative social and economic implications. The unfortunate outcome is that intended results are rarely achieved, but scarce funds are misallocated and unnecessary hardships are heaped upon those segments of society that become scapegoats for flood-related disasters and damages.

It then adds:

Contrary to popular belief, forests have only a limited influence on major downstream flooding, especially large-scale events. It is correct that on a local scale forests and forest soils are capable of reducing runoff, generally as the result of enhanced infiltration and storage capacities. But this holds true only for small-scale rainfall events, which are not responsible for severe flooding in downstream areas. During a major rainfall event (like those that result in massive flooding), especially after prolonged periods of preceding rainfall, the forest soil becomes saturated and water no longer filters into the soil but instead runs off along the soil surface.

For a brief update on the FAO’s report, see here.

Other resources:

USDA Forest Service (2007), New Mandala (2011) with this article, U.K. Forestry Commission on both sides of the debate, Latin American experience.


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27 02 2012
Royalist fundamentalism « Political Prisoners in Thailand

[…] rampant consumptionism. He thinks “excessive consumption” is a cause of global crises. Like the king, he talks of “greed.” Remember that this is a man who is taken about in light yellow […]

27 02 2012
Royalist fundamentalism « Political Prisoners of Thailand

[…] for its rampant consumptionism. He thinks “excessive consumption” is a cause of global crises. Like the king, he talks of “greed.” Remember that this is a man who is taken about in light yellow luxury […]