It is the most disasterous cyclone-hit in recent times. Latest reports suggest 22,464 people confirmed dead with another 41,054 missing, mostly in the low lying Irrawaddy delta region on the Burmese coast, where those still alive are facing deficits of foot, water, shelter and sanitation. The damage was done not by the winds of "Cyclone Nargis" however, but by a tidal surge more than ten feet high that swept across the land. It's tempting to attribute such disasters to bad luck, but in fact this was at least partly preventable, and scientists explained exactly why in 2005 in the research that I'll show you now - Dahdouhguebas et al's "How effective were mangroves as a defence against the recent tsunami?" [1].

Mangroves have long been believed to act as a useful barrier against the movements of tides, largely because of their large, tangled, above-ground root systems. Unfortunately, human activity in the 20th century has resulted in around half of the world's mangrove forests being destroyed, with a slowing but still substantial loss rate today [2].

I very carefully used the word "believed" in the last paragraph rather than "known". While common sense and anecdotal evidence does suggest that mangrove forests act as buffers, there was - until recently - suprisingly little empirical evidence to back that assumption up. The authors of this paper sought to address that gap in our knowledge by studying the after-effects of a recent major flooding event - the now infamous Asian Tsunami.

The extent of the flooding (NASA).

The team's work was made possible by the fact that they had already conducted substantial surveys of the affected region in 2001, giving them a good picture of the position, extent and "naturalness" of mangrove forests and the communities that lived along-side them. In 2005, shortly after the Tsunami had hit, they were able to go back and visit 24 coastal areas on Sri Lanka (a hard-hit area that had suffered over 23,000 deaths), to assess the damage caused and look for any correlation between damage mitigation and mangrove prevalence.

It turned out that natural Mangrove forests were amazingly resilient to the effects of the waves: "Our results show that ... apart from some isolated trees ... there were no records of uprooted adult mangrove trees. At most, mangrove fringes near the water edge took all the energy and were damaged. Creekfringing Nypa fruticans (Mangrove palm) had its leaves bent or torn off, but anchoring protection of this plant by its rhizomatous stem allowed new young leaves to emerge less than a month after the tsunami impact."

Considering the sheer destructive force unleashed by the Tsunami, this is a pretty amazing finding. More importantly, the mangrove forests had protected local communities: "Our surveys of villages and post-tsunami observations make it clear that mangroves play a critical role in storm protection, but with the subtle point that this all depends on the quality of the mangrove forest. The conversion of mangrove land into shrimp farms, tourist resorts, agricultural or urban land over the past decades ... have likely contributed significantly to the catastrophic loss of human lives and settlements during the recent tsunami event."

Just how many lives could be saved by better coastal planning is illustrated by an example the BBC have raised today: "Researchers from IUCN, formerly known as the World Conservation Union, compared the death toll from two villages in Sri Lanka that were hit by the devastating giant waves. While two people died in the settlement with dense mangrove and scrub forest, up to 6,000 people lost their lives in a nearby village without similar vegetation."

That this situation has increased the death toll in Myanmar this week has been suggested by leading politicians in the region. ASEAN secretary-general Surin Pitsuwan is quoted by AFP (via the BBC) as saying of the current disaster that, "encroachment into mangrove forests, which used to serve as a buffer between the rising tide, between big waves and storms and residential areas; all those lands have been destroyed. Human beings are now direct victims of such natural forces."

And so yet again we see an example of how environmental degradation can lead directly to the destruction of communities and loss of life, and I find myself wondering just how many times things like this need to happen before governments finally understand how spectacularly dangerous poor planning policies can be. It's a frustrating message to keep repeating, but perhaps now it has been learned by at least one nation. That won't bring back the 20-odd thousand dead people though.

[1] DAHDOUHGUEBAS, F., JAYATISSA, L., DINITTO, D., BOSIRE, J., LOSEEN, D., KOEDAM, N. (2005). How effective were mangroves as a defence against the recent tsunami?. Current Biology, 15(12), R443-R447. DOI: 10.1016/j.cub.2005.06.008

[2] Alongi, D.M. (2002). Present state and future of the world’s mangrove forests. Environ. Conserv. 29, 331–349.