By T V Padma Some glad tidings from the bleak field of climate change science. New research from the Indian Institute of Technology (IIT), Kharagpur, shows that a majority of Indian forests are exceptionally resilient to large variations in rainfall and short droughts caused by climate change. The research, which used canopy cover and rainfall changes as criteria to deduce resilience, revealed that forests in wetter regions and scrubs in drier regions would be more resilient to rainfall decline. Scientists use climate and vegetation models to predict the impact of global climate change on Earth’s ecosystems. In this case, the IIT study compared long-term trends in spatial distribution of Indian forests, against corresponding rainfall records. This inquiry of how India’s vegetation cover responded to precipitation between 2000 and 2017 provided positive news — forests have been surprisingly resilient to changing rainfall patterns. This novel research has generated a “forest cover resilience map” which could be used to frame uniform and improved climate-adaptive conservation and management policies in India. Interestingly, the study provides a “precipitation threshold” of forest cover resilience — which helps scientists estimate the tipping point beyond which a forest cannot easily recover. They claim that forest cover would remain resilient at rainfall levels over 1400 millimeters per year. But do these findings reflect ground reality?

This tropical lowland rainforest from Agumbe in the Karnataka Western Ghats can withstand large changes in rainfall patterns. Photo by Anand Osuri/ Wikimedia Commons.

Previous studies at both the national and regional levels have indicated that forest grids spread across India are vulnerable to climate change. In the state of Uttarakhand, for instance, up to 80 percent of forest has been shown to be sensitive to climate. “This is a very significant result but it is drawn by considering only one, that is, precipitation, of the several factors such as temperature, soil, and anthropogenic influences that have a major influence on existence and sustainability of forests at a location,” observes Jagmohan Sharma, additional principal chief conservator of forests, Bengaluru. Can our forests survive climate extremes? The team from IIT studied the survival probability of forests and other vegetation types in a changing climate regime. They used open source data on tree canopy cover percentage to map the spatial distribution of forest, scrub, grassland and treeless areas in India, and assessed their links with long-term annual rainfall. Natural forests were found in areas with 340 to 8650 millimeters rainfall, scrubland in areas with 196 to 1018 millimeters, grassland at 167 to 995 millimeters and treeless areas at 34 to 965 millimeters rainfall. The scientists reported in the journal Biodiversity and Conservation that only 0.02 percent of the total forest cover in India — in the dry regions of the Trans-Himalayas — was estimated to be “least resilient”. Forest in wetter areas such as the Western Ghats, Western Himalayas, Eastern Ghats and Northeast India are predicted to be “highly resilient”. So, the “majority of forest covers in India are extremely resilient” to large precipitation changes in addition to the shorter drought periods. In contrast, scrubland was estimated highly resilient in drier regions and least resilient in wetter regions. The scientists also stated that the “forest cover resilience curve saturates about 1400 millimeters precipitation”, which indicates that forests would be resilient at rainfall levels of over 1400 millimeters while the scrubs would not be very resilient. For example, if a forest regime receives 3000 millimeters precipitation on average, a decrease or increase in precipitation by 500 millimeters may not change its resilience by much. However, if another regime receives 1500 millimeters, the same change of 500 millimeters rainfall would impact the resilience “significantly”, Pulakesh Das, one of the study authors, explained to Mongabay-India. Therefore, forests in the drier landscapes may experience alterations due to climate change. “Although the seasonal dry tropical forests in the Deccan Peninsular region are tolerant to drier periods or drought events to some extent, they are the most vulnerable forests to large changes in climate,” he said.

Forests in drier regions such as this one from the Sri Lankamalleswara Wildlife Sanctuary in Andhra Pradesh are most vulnerable to climate change. Photo by P Jeganathan/Wikimedia Commons.

A girl climbing Quercus lanuginosa tree to cut fodder in Askot Wildlife Sanctuary. Photo by A. J. T. Johnsingh, WWF-India and NCF/ Wikimedia Commons.

His team’s study, using ensemble climate data from five climate models and two global vegetation models suggests that the current forest in more than a third of forest grid cells in India will undergo shifts due to climate change, and current forests status would no longer be applicable then. Also, current model-based assessments do not take into account non-climatic factors such as cattle grazing and man-made fires that can “dramatically modify the impacts under climate change.” That said, Sharma’s team too concurred with Das’s findings that forests in higher rainfall zones are less likely to be impacted by climate change than drier forests. In dry regions there will be a double impact, said Das. There could be a loss of forest cover due to less rainfall and “in dry regions, the rate of forest cover recovery would be slower,” he warned. Kumar mentioned that national-level studies for such inferences are limited and scientists need to adopt varied approaches, including testing of multiple vegetation models under multiple climatic scenarios, to communicate findings with more confidence. “We also need to develop regional vegetation models that could give the prediction at finer resolution with greater accuracy,” he added. And ensemble models using a mix of various prediction models, could provide a more comprehensive picture. Banner image: Wet forests such as those in Namdapha Tiger Reserve, Arunachal Pradesh, Northeast India are highly resilient to climate change. Photo by Rohit Naniwadekar/ Wikimedia Commons. *** This article was originally published on Mongabay.com. Mongabay-India is an environmental science and conservation news service. This article has been republished under the Creative Commons licence.