- Efforts to plant trees in savannah grasslands can harm biodiversity and affect soil carbon storage, says field ecologist Mahesh Sankaran.
- Mahesh Sankaran received the 2021 Infosys Prize in Life Sciences for his research on the ecology of tropical savanna ecosystems and policy expansion through his work with two intergovernmental science and policy bodies.
- Long-term efforts that capture slow or episodic processes such as the effects of drought on ecosystems are crucial to understanding how an ecosystem responds to climate change.
More than two decades since he began unraveling the mysteries of the tropical savanna – open grasslands with sparse trees – field ecologist Mahesh Sankaran remains fascinated by these ecosystems, which he refers to as a “complex web of interactions” between climate, fire, herbivores and plants.
Sankaran was recently awarded the 2021 Infosys Prize in Life Sciences for his “pioneering work in the ecology of tropical savanna ecosystems, his contributions to highlighting the biodiversity of important Indian ecosystems such as the Western Ghats, and his contributions to international reports on climate change and biodiversity that have provided scientific evidence for policy makers.
According to Sankaran, protecting and restoring grasslands in India that have been compromised by reckless tree planting for climate mitigation and clean energy initiatives can offer a win-win solution for biodiversity conservation and climate mitigation.
In an email interview with Mongabay-India, he advocated sustainable funding for long-term research critical to understanding how savanna ecosystems respond to climate change, emphasizing that context-specific nature-based solutions can play a role in mitigating climate change. , but it is not a panacea and “is unlikely to contribute to mitigating climate change if we do not significantly reduce greenhouse gas emissions first”.
“Planting trees in these systems (grasslands) not only threatens local biodiversity, reduces grazing potential and alters hydrological cycles, but can sometimes lead to soil carbon loss. When it comes to grasslands, a ‘win-win’ solution for both conservation on biodiversity and climate mitigation, is the protection and restoration of the country’s grasslands and the ecosystem services they provide to the human communities that depend on them.” The Ecology of Ecosystems Laboratory at the National Center for Biological Sciences (NCBS), Bengaluru.
He emphasized that although grasslands may not store much carbon above ground, they can support large stores of carbon underground. Globally, soils store up to three times more carbon than aboveground materials, and it is estimated that 30% of soil carbon stocks are in grasslands.
Sankaran earned his undergraduate degree in computer science, eventually choosing a career in ecology and wildlife biology. It reiterates a key warning from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) and the Intergovernmental Panel on Climate Change (IPCC) – Report of the Workshop on Biodiversity and Climate Change: Climate mitigation cannot come at the expense of sustaining Biodiversity .
“This is a particular challenge when it comes to grasslands in India because they are indiscriminately targeted for tree planting for climate mitigation and clean energy initiatives,” said Sankaran, one of the report’s authors. For example, planting monoculture dense trees in grasslands and savannahs as a carbon sequestration measure could have “disastrous unintended consequences” in terms of loss of diversity of native and endemic species.
There is currently little evidence to suggest that tree-planting efforts in India have led to increases in the country’s green cover, Sankaran stresses, recommending that restoration targets (26 million hectares) should be ensured as part of the Bonn Challenge. focus on reforestation (planting trees in areas that previously supported trees) rather than afforestation (planting trees in areas where they were not previously present, such as grasslands); Afforestation can lead to deterioration rather than bringing back green cover.
Moreover, the right trees should be planted in the right places supplemented with regular monitoring and care for the planted seedlings with community participation to improve the quality of restoration efforts. “It would be prudent, and cost-effective, to set goals on a smaller scale that are locally achievable, and to involve local communities who can be long-term sponsors of these efforts.”
Need a “greater appreciation” of savannas and grasslands in biodiversity conservation and climate mitigation
After delving into the intricacies of the savannah ecosystem, Sankaran called for a “greater appreciation” of the role that savannas and grasslands play in protecting India’s biodiversity, including some of the last remaining populations of many charismatic but endangered species (such as the Great Indian Houbara, wolf and hyenas). , etc.), their strong cultural ties with many societies, and their contribution to underground carbon sequestration.
His experiences outdoors growing up, reading about wildlife and wild nature (“whatever I can get my hands on”) and trips to protected areas during his college days as a computer science major, piqued his interest and shaped his decision to pursue a career in ecology and biology. Wild, “although at the time the options were very limited in India,” Sankaran recalls. Completed a Ph.D. He received his PhD from Syracuse University in the US and did post-doctoral research in both the UK and the US before joining NCBS in 2009.
The field ecologist focused on the savannah grasslands of the Kalacad-Mondanthurai Tiger Reserve in the Southwest Ghats for his Ph.D. Research, charting a profession researching the African and Indian savannahs using a range of methods including experimental manipulation, surveys, data synthesis and long-term observation.
But why tropical savanna ecosystems? “If you are interested in megafauna, as I am, then Tropical Savanna Ecosystems is the place for you. They support amazing assemblages of large herbivores and the greatest diversity of large herbivores and carnivores on Earth,” notes Sankaran.
The scientist was also inspired by his Ph.D. thesis. Consultant American ecologist Sam McNaughton, realizing that these seemingly simple open ecosystems were, in fact, a complex web of interactions between climate, fire, herbivores and plants. McNaughton is best known for his work on the relationships between plants and herbivores in the Serengeti. “I have since worked with many wonderful colleagues and collaborators — savannah experts from around the world — who provide different insights and perspectives that continue to intrigue and continue to interest me,” he said.
The savannah biome is vast and covers about 20% of the global Earth’s surface, supporting nearly a fifth of Earth’s population, most livestock, and the greatest density and diversity of land herbivores and carnivores. Sankaran explains that the savannas of Africa, South America, Australia and Asia look very similar but are functionally very different.
For one thing, they are found in different climates, and on the other hand, they are also affected by processes such as fire and herbivores to different degrees. “The African savanna, however, is the closest analogue to the Indian savanna – they share a common evolutionary history. [many of the dominant tree species in both continents belong to the same genera such as Vachellia (earlier Acacia) and Terminalia]. “
Both are distinguished by the presence of diverse and abundant aggregations of large herbivores, unlike the savannas of Australia and South America. While both antelopes and deer make up the ungulate community in the Asian savannah, the African savannah is characterized only by antelopes (there are no deer in sub-Saharan Africa). Also, on average, the Asian savanna tends to be slightly wetter than the African savanna.
His work attests to the susceptibility of these ecosystems to climate change, habitat loss and land degradation, revealing that “tropical savannas are more complex than previously recognized and that multiple factors beyond climate influence their ecological status.” But information about it is often misleading.
Sankaran expands on this misinformation stressing that tropical grasslands and savannas are ancient ecosystems that evolved 5-8 million years ago, consistent with the simultaneous global expansion of tropical grasses around the world. “Thus they are not degraded forests, or ‘barren lands’ to be targeted for climate mitigation or poorly designed afforestation programmes. They support unique biodiversity and can be rich in species in some cases. Furthermore, fire is not a bad thing in Grasslands – it is an inherent feature of grasslands and savannas, and in these systems, the lack of fire rather than combustion is a major problem.”
The importance of a long-term search for the savannah
Sankaran at NCBS has worked on Climate Change and Trans-Himalaya Grassland Dynamics in Spiti, Himachal Pradesh, and Sikkim on long-term system monitoring (“continuous existence and immersion in a system”) because many ecological processes are slow or usually miss these episodic and short-term studies .
Let’s take the case of drought, for example. One cannot fully understand how drought affects ecosystems through short-term studies conducted during or immediately after drought. In such cases, pre-drought data are usually not available, so one cannot quantify the magnitude and nature of the ecosystem response. Furthermore, there are often lags between when an event occurs (drought) and when responses (such as tree death or impacts on fire systems) appear, again emphasizing the need for long-term studies.”
With ongoing and ongoing funding a ‘key issue’ in long-term research programs in India and the world, he is encouraged to see the Ministry of Environment, Forests and Climate Change initiate the Long-Term Environmental Observatories (LTEO) program on long-term research of species and ecosystems across the country. “We hope this will catalyze other similar funding efforts for much-needed long-term work in India,” Sankaran adds.
Banner picture: Pig deer in the towering pastures of Terai, Kaziranga, Assam. Photo by TR Shankar Raman.