[RIO DE JANEIRO] A study indicates that Latin America's woody vegetation increased in dry shrubland ecosystems over the period 2001–2010, particularly in northern Mexico and northeastern Brazil — despite previous research revealing deforestation trends in these areas.
The study, published in Biotropica on 3 August, is the first to analyse regional deforestation and reforestation simultaneously.
Using satellite data, researchers surveyed forest coverage in over 16,050 municipalities within the 45 countries of Latin American and the Caribbean. They also analysed the relationship between woody vegetation changes and demographic and environmental variables, such as migration and urbanisation.
As expected, deforestation is still the dominant process: there was a vegetation loss of nearly 542,000 square kilometers in the period 2001–2010.
On the other hand, researchers observed reforestation in approximately 362,000 square kilometres, mainly in regions too dry or steep for agriculture. Importantly, the study revealed that more than 40 per cent of woody vegetation expansion occurred in the desert or xeric [very dry] shrubland areas.
T. Mitchell Aide, a biology professor at the University of Puerto Rico and the study's lead author, told SciDev.Net that reforestation often occurred in large deforested areas, which are barely used, therefore enabling a small proportion of the area to recover naturally.
However, he said he had seen no evidence that the reforestation process had been stimulated by conservation policies or direct human intervention.
"Colombia […] had the highest level of reforestation, [mostly] in the Andes," Aide said. "In this region, violence was an important factor, causing the migration of millions of rural inhabitants. It seems that in most areas, reforestation is an indirect effect of socioeconomic change".
In desert shrublands in Brazil and Mexico, demographic factors — as well as increased rainfall levels — led to forest increase: in Mexico, violence associated with the illegal drug trade was a strong factor, while in northeastern Brazil, the decline of agricultural activity in the Caatinga region played a key role.
However, it will be years before the new forests support as much flora and fauna as undisturbed areas.
"This is an important and useful study," said Dominick Spracklen, research fellow at the University of Leeds. "However, I don't think it is clear what is occurring in these regions". For example, he says, it is likely that greater regional rainfall over the past decade could be part of a potentially reversible natural cycle, rather than a long-term trend.
"The relative coarseness of the satellite observations used here is also a potential issue that the authors themselves highlight," adds Spracklen. "Such coarse resolution data can miss small-scale agriculture and forest degradation, meaning that gross deforestation rates might be underestimated. It also makes it more difficult to identify what is causing the increase in woody vegetation."
Biotropica doi: 10.1111/j.1744-7429.2012.00908.x (2012)