- A vegetation assessment of India’s tiger reserves suggests that the elevated protection status of reserves alone is insufficient in preserving the vegetation conditions.
- The study finds extensive browning and drying of vegetation in over 50% of the 29 tiger reserves assessed.
- Just less than 50% TRs fared better in vegetation condition than the wildlife sanctuaries the TRs were compared to.
- The main limitation of the study is it uses only remote-sensed data without incorporating any data based on the on-ground situation, other researchers said.
A vegetation assessment of India’s tiger reserves suggests that the elevated protection status of reserves alone is insufficient in preserving the vegetation conditions. This casts doubts on the effectiveness of the protection status in safeguarding the long-term future of tiger reserves in the country.
In India, how well Protected Areas (PAs) fare is measured by the estimates of ‘umbrella species’ like the tiger, the lion, or other charismatic large animals. Or it is measured on management considerations of the legal status of the PA, the strength of workforce employed, instances of man-animal conflict, among others.
Tiger Reserves (TRs) are bestowed with the highest levels of protection under the protected areas network. They are governed by the ‘umbrella species’ concept of conservation management, where the top predator, in this case the tiger, is the umbrella or flagship species. The idea is that while protecting the habitat for the top predator, other species also get protection along with the habitat itself.
But what if this idea isn’t the reality on the ground?
There are few estimates for most of the other species, apart from the tiger, in Indian PAs. And fewer for the condition of the forests itself.
A recent study aims to correct this record. The study is probably the first scientific assessment of the condition of the vegetation in India’s tiger reserves.
“The motivation behind this study is to check for the vegetation condition which is one of the promised beneficiaries of the umbrella species management concept,” said Pradeep Koulgi, an ecologist with Centre for Wildlife Studies (CWS), who carried out the analysis.
“In India, the emphasis is so heavily placed on tigers being the measure of success or failure of protection that we feel we need to expand and move away from what we are looking at,” said Krithi Karanth, Executive Director at CWS, who was also involved in the study.
The study finds extensive browning and drying of vegetation in over 50% of the 29 TRs assessed. And just less than 50% TRs fared better in vegetation condition than the wildlife sanctuaries the TRs were compared to. These results, according to the study, suggest that the elevated protection status of the TRs alone is insufficient in preserving the vegetation condition.
“This study is useful as it draws attention to an important issue on the effectiveness of PAs,” said Robert John Chandran, a scientist at the Indian Institute of Science Education and Research (IISER) in Kolkata. “It also brings more clarity on the fact that some TRs may have held up better than others.” Chandran wasn’t involved in the study.
According to Karanth, the study shows “that there are other ways of monitoring the PAs and evaluating protection.” She reckons that the long-term monitoring of vegetation is particularly important over time and scale throughout the country regularly. “So that we can have some idea about what is a healthy forest.”
For their analysis, the researchers selected 29 TRs declared in the year 2000 or earlier. These reserves span the five management clusters of Central India, North East Hills, Shivalik – Central India, Shivalik – Eastern Ghats and the Western Ghats.
The team analysed remotely sensed data spanning nearly three decades (1984-2012) for the tiger reserves, from Google Earth Engine. This allowed the researchers a ten-year period, as the first set of TRs were declared in 1972, for estimating the condition of the vegetation post-declaration for all TRs. For some of the TRs the researchers could assess both pre and post-declaration conditions.
The researchers also matched each TR with a wildlife sanctuary (WLS) in the same state as the TR, receiving an average annual rainfall within 500 mm from the TRs. They selected the WLS that was nearest to the TR. To account for historical context in the changes of the vegetation condition, the team considered the WLS as the control and the TR as the impacted area.
“We wanted to do this control-impact comparison to see what heightened protection measures have done for tiger reserves while a comparable forest patch nearby didn’t get that treatment,” says Koulgi. In other words, “Did the tiger reserve really benefit?”
Vegetation condition is commonly measured by vegetation ‘greenness’ and moisture content. The team considered annual brownest and driest values, typically represented in peak summer, to calculate the vegetation condition.
The hypothesis was – being designated as TR would be beneficial to the vegetation condition due to two reasons. One, with more investment in patrolling and decreased human disturbance, vegetation degradation would reduce. And two, under the ‘umbrella-species’ management practices, vegetation condition would stand to gain indirectly.
“The question is – does this translate to promised benefits, which in this case is improved vegetation condition?” asks Koulgi.
On the basis of the declaration year of the TR, time period for each TR and its paired WLS was divided into “before” and “after” epochs. Based on the brownest and driest values, vegetation condition after TR declaration was classified as “improve,” “decline,” or “unclear.”
Calculating the percentage of PA-area under each of these categories gave the team PA-wise accounts of composition of vegetation condition. After the TR declaration, its vegetation condition was categorised as “helped,” “harmed,” or “unclear” based on the brownest and driest values from before and after epochs.
The results show improvement in vegetation condition (in more than half of their area) in only two TRs – Satpura and Bandipur – in the years after being declared as TRs. More than 90% of Bandipur’s area improved. In 13 TRs, vegetation condition declined in more than half of their area. In six TRs of Bandavgarh, Panna, Corbett, Pench, Tadoba and Indravati, the decline was in over 75% of their area.
As compared to their WLS pair, a greater percentage of the area improved in 12 TRs. On the other hand, the vegetation condition worsened in 8 TRs, with a larger percentage of area in decline as compared to their paired WLS.
In four TRs, the vegetation condition was helped in more than 25% of their area, while in five TRs the vegetation condition was harmed in the same size of area. Satpura and Pench saw vegetation condition harmed in more than 50% of their area.
The main limitation of the study is it uses only remote-sensed data without incorporating any data based on the on-ground situation. “The study could have analysed the trends in each TRs to understand more clearly what is happening in each TR and WLS,” according to Chandran.
But such data is hard to come by at the scale which this study was carried out. “That is the inherent limitation of the (administrative) system,” said Koulgi. “It is important to consider some more planning in the direction in facilitating these sort of analysis as these are premier forest areas in the country with a lot of resources are spent on them.”
CITATION:
Koulgi, P.S., Clinton, N. & Karanth, K.K. Extensive vegetation browning and drying in forests of India’s Tiger Reserves. Sci Rep 9, 14976 (2019) doi:10.1038/s41598-019-51118-8
Banner image: A tiger camouflaged by dry grass in Tadoba-Andheri tiger reserve. Photo by Eeshan Sonak / Wikimedia Commons.
