Trees alone don’t make a forest
Global mappings of cover may not always reveal the true story
Anew study published in Nature has said the global tree canopy cover has increased by 2.24 million square kilometres between 1982 and 2016. Using satellite data, researchers from the University of Maryland, State University of New York and NASA
ourtake Goddard Space Flight Centre found that the gains made in forest area in the temperate, subtropical, and boreal climatic zones are neutralising the decline that is taking place in the tropics. Interestingly, the study adds, forests in mountain regions are expanding as climate-warming enables trees to grow higher up on mountains. The important finding is that much of the change is nevertheless anthropogenic; climate change-induced vegetation growth is a smaller fraction.
The study, however, has the same limitations that exist in India’s State of Forest reports because it maps “all tree cover” under one category. The Nature study uses three land-cover categories: tree crops; short vegetation cover; and bare ground. The issue with such categorisation is that “tree crops” could be anything: natural forest, teak plantations, or eucalyptus plantations. Second, the reported expansion of “tree cover” is happening in temperate countries, including temperate parts of China but not so much in the tropics or part of the subtropics.
Last, but not the least, one must keep in mind what makes a forest. It is not just the number of trees, but the biodiversity that it nurtures, and so one must always be aware of the difference between forest cover and tree cover. Since 2003, India has lost over 1,000 sq km of dense forest every year, and compensated roughly half of that with plantations. Such additions only look good on paper. The same is happening in China where the government has launched a massive tree-planting exercise . The tree cover is largely single species, not necessarily native to those regions, and coercive in its creation. Unfortunately, these issues or the impact of such single species (which has a cascading effect on the ecosystem), are never captured in global mappings such as the one published recently in Nature.