Sep 1, 2016
Deforestation boosts tropical floods
Deforestation has increased the occurrence of flooding in Indonesian Borneo over the past 30 years, according to researchers in Australia and Indonesia.
Based on interviews with local villagers and articles from local media sources, the study shows that, in just three years, upwards of 750,000 people from hundreds of settlements were displaced by flooding. Those affected are more likely to have come from regions deforested for mining and oil-palm plantations, the researchers say.
"The relationship between land cover and flooding occurrence in the tropics remains unclear, primarily because the data to study these relationships are difficult to obtain for large geographic scales," said Erik Meijaard of the University of Queensland. "Our study shows that deforestation does increase the frequency of flood events – and this is important in broader sustainable development planning, where often the benefits of deforestation are quite well known but not the costs."
Flooding is a major concern in tropical countries but in the past scarce data has prevented researchers from determining the causes. In Indonesia, says Meijaard, the government collects data on floods and other hydrological variables, but the data are not consistently compiled. Worse, they often go missing.
To get around this problem, Meijaard and colleagues collected data in the form of interviews with village leaders and newspaper clippings. "This is not new in itself, but as far as we know it has not been applied to model environmental disasters such as floods across large geographic scales," said Meijaard.
Meijaard’s group estimated the frequency of floods, and whether this had changed over the past 30 years, based on interviews with the leaders of more than 360 villages in Indonesian Borneo. The researchers also collated reports of flooding from the archives of 16 news agencies over three years, to show where flooding occurred and whom it affected. Finally, they analysed all the data using computer models.
The team found that flooding in Indonesian Borneo has been far more widespread and destructive than government assessments had previously suggested. The news articles indicated that between 776,000 and 1.5 million people – 5–10% of the population – have been displaced from more than 860 settlements. Meanwhile, the interviews suggested that the frequency of flooding is linked to land use in the catchment areas, with those areas suffering deforestation from mining and palm-oil plantations being more likely to be affected.
"Our two data sources – newspaper analyses and community interviews – are independent, but the resulting spatial predictions of floods and flooding trends are very similar," Meijaard pointed out. "This suggests that our methods are reliable."
That is good news for researchers like Meijaard, who will now be more confident in performing analyses with data from multiple sources. As for Indonesian Borneo, the researchers recommend that the risks of flooding be taken into account in future planning decisions.
Meijaard’s group is now attempting to quantify the societal and economic costs of flooding due to deforestation. "Translating risks into actual economic costs should help convince governments to more seriously consider land-use decision impacts," said Meijaard.
The study is published in Environmental Research Letters (ERL).
- Rising floodwaters: mapping impacts and perceptions of flooding in Indonesian Borneo Jessie A Wells et al 2016 Environ. Res. Lett. 11 064016
- Erik Meijaard
About the author
Jon Cartwright is a contributing editor to environmentalresearchweb.