- Mizoram University scientists have identified two tree species that could be planted in shifting cultivation fallows to speed up their regeneration into secondary forests and enhance carbon sinks.
- The study finds that fallow age contributed the most to the recovery of carbon. The findings are in agreement with other studies in the region. Abandoned fallows are also known to have a high potential for carbon storage.
- Secondary forests are gaining importance in the tropics as pristine forests are cleared. And it is vital to understand the impacts of changing patterns of shifting cultivation on carbon storage.
Chestnut and olive trees that occur naturally in the wild in Manipur have the potential to speed up fallow regrowth in shifting cultivation (jhum) sites and enhance carbon sinks as the fallows regenerate into secondary forests, according to a study.
Olive (Elaeocarpus floribundus Blume) and chestnut (Castanopsis hystrix) can be collected from the surrounding forests or germinated and planted in jhum fallows to accelerate natural succession, said Mizoram University researchers who identified the two species that strike roots in early fallows.
The study’s corresponding author Uttam K. Sahoo of Mizoram University told Mongabay-India that fallow age was the key contributor to carbon recovery in fallow stands. Experts suggest the successful implementation of carbon-based payment for ecosystem services (PES) schemes, such as REDD+ (Reducing Emissions from Deforestation and Forest Degradation), can also conserve landscape-level carbon stocks and biodiversity in shifting cultivation landscapes.
Researchers measured tree height and girth at four shifting cultivation fallow lands (left unplanted for 5, 10, 15, and 20 years) owned by local community members in Ukhrul and Chandel districts of Manipur. Ukhrul is located at an elevation of 1662 metres above sea level and Chandel at 957 metres. They estimate that “it will roughly take 39 to 41 years for the regenerated fallows to store equal carbon as that of an undisturbed forest.”
In their Manipur site, researchers found that the slope, aspect (positioning of the fallows), and elevation were responsible for the increase in the number of trees with the increase in the number of years the land remained uncultivated (fallow). The size of the tree also increased with increasing fallow age.
Forest recovery increased with increasing elevation and that’s why the percent recovery of tree species from 5 years fallow to 20 years fallow was more in Ukhrul (located at a higher altitude) than in Chandel. This is because high altitude species have great potential to adapt to diverse micro-climatic situations as high elevation forests are generally open forests and therefore have more ability to recruit in the deforested areas.
Joli R. Borah who researches on sustainable management of agricultural landscapes for biodiversity conservation and human well-being agrees with the findings that fallow age was found to have contributed the most to the recovery of carbon.
“As fallows regenerate in shifting cultivation, they sequester carbon stocks in recovering biomass,” said Borah, who was not associated with the Manipur study. Borah, a postdoctoral research fellow, Faculty of Forestry, University of British Columbia, told Mongabay-India that previous studies from elsewhere including her research in Nagaland have also shown that fallow age is the most important factor in carbon stock recovery in shifting cultivation landscapes.
Farmers are also applying innovative ways to bolster forest regeneration ( rapid carbon recovery) and improve crop production. In Nagaland’s Khonoma village, for example, the Angami Naga tribe innovated the Alder coppicing system by retaining and pollarding nitrogen-fixing Alder trees that facilitate fallow regrowth, she adds.
The dynamic nature of shifting cultivation, an agricultural system practiced for centuries, results in a landscape mosaic of jhum fields, secondary forests, and old-growth forests. Many forests in northeast India are secondary forests at different stages of succession following shifting cultivation. These forests are an essential source of rural livelihood and also for multiple environmental functions such as soil and watershed conservation, flood control, and carbon storage, the authors underscore.
In northeast India, an area of 8500 square kilometers is still being used to practice shifting cultivation, revealed a 2018 report released by the Indian government think tank NITI Aayog. But the promotion and expansion of settled agriculture such as terrace farming and plantations have come at the cost of regenerating fallows, which would otherwise have regrown into secondary forests.
The resultant land-use change has long-term implications, leading to a loss of vital ecosystem services and land degradation, according to the report.
Sahoo observes that while northeast India has been a “huge contributor” to greenhouse gas emissions due to deforestation, adapting proper land-use systems will help recover biomass carbon stock in the forests. Secondary forests, such as recovered fallow stands, are gaining importance in the tropics as pristine forests are cleared. “Over the years, it is accepted that regrowth forests in the tropics provide similar ecosystem goods and services as old-growth forests,” he pointed out, clarifying that shifting cultivation is an old concept built around the temporary removal of trees “but not of the forest.”
Impacts of changing patterns of shifting cultivation on carbon storage
Borah reiterates while the recent trends of reducing fallow period and expansion to the primary forest in shifting cultivation contribute considerably to carbon emission and biodiversity loss in the tropics, at the same time, this traditional practice of cultivation also plays an important role in ensuring food security by providing subsistence to 200-300 million people across the world.
“With this marked and increasing contribution of shifting cultivation to forest transformation, it is vital to understand the impacts of changing patterns of shifting cultivation on carbon storage and to develop strategies to reduce carbon emission while maintaining crop yield in these landscapes,” she said.
In the last few decades, the state policies in northeast India viewed shifting cultivation as a primitive, inefficient (due to low yields) and environmentally unsustainable practice (due to deforestation, forest degradation, and soil erosion) and provided incentives for settled agriculture and perennial cash crops, noted Borah. Holding that there is a need to change the prevailing negative perception of jhum, Sahoo emphasises understanding secondary succession and the ecosystem services associated with it.
Borah spelled out legislations such as the Jhum Land Regulation act (1948) and National Forest Policy (1952) aimed at rehabilitating shifting cultivation and promoting terrace cultivation, animal husbandry, horticulture, permanent agriculture, and cash crop cultivation (coffee, tea, black pepper, teak, and rubber). Various schemes such as ‘Control of Shifting Cultivation (1976-1977)’ and ‘Purchase of Land for Rehabilitation of Jhumias and Land-less Tribal (1985-86)’ tried to resettle jhum farmers in arable land across the northeastern states.
In contrast to the perceptions that motivated government initiatives to replace shifting cultivation, scientific evidence, Borah pointed out, suggests that it is well adapted to heavy rainfall and environmental conditions in mountainous regions and less harmful for the environment and biodiversity compared to permanent agriculture (e.g. oil palm or rubber plantation). Abandoned fallows are also known to have a high potential for carbon storage. In fact, as Sahoo notes, some studies have shown higher species richness, soil, and water holding capacities, carbon stock in abandoned fallows than other permanent agriculture.
While assessing how the declining fallow period affects carbon stocks in shifting cultivation landscapes, and the land-use strategies that can boost landscape-level carbon under REDD+ in Nagaland, Borah, and co-authors found that carbon stocks recover substantially as the secondary forest regenerates following shifting cultivation, with a 30-year fallow storing about half the carbon of an old-growth forest.
Recent state policies, such as the Shillong Declaration 2004 and National Mission on Greening India, have tried to move away from the negative perceptions and to improve shifting cultivation rather than replacing it. “Nagaland Environmental Protection and Economic Development (NEPED 2002) has successfully incorporated farmers’ innovations such as contour hedgerow intercropping (growing nitrogen-fixing shrubs as dense hedgerows along slope contours and planting crops between the hedgerows) into its programs,” observed Borah.
Farmers in different parts of northeast India are “adapting various innovative ways to enhance forest regeneration (i.e., rapid carbon recovery) and improve crop production.”
“They have innovated techniques in various stages of the cultivation process, such as clearing, cropping and fallow management such as preventing soil erosion by using wooden logs and cover crops, managing fallows by retaining plants that aid in faster fallow and soil recovery and in some instances avoid burning by adopting slash and mulch system,” she elaborated.
However, there are still challenges in incorporating the complex and dynamic nature of shifting cultivation with its transition from farmland to regenerating forest during a cultivation cycle. “During the cropping phase, it is often considered as agriculture and the same piece of land is categorised as ‘abandoned land’, ‘wastelands’ or ‘Unclassed State Forests’ during the fallow phase. This ambiguity leads to the same piece of land falling under different laws, regulations, and management.”
“To address this effectively, policies need to adopt a landscape-scale approach by integrating the inherent mosaic nature of this cultivation system with various land uses and ensure cooperation between different ministries such as the Ministry of Environment, Forest and Climate Change and Ministry of Development of North Eastern Region,” Borah said.
A recent study had pointed out that in the West Garo Hills district of Meghalaya, shifting cultivation is the most extensive land-use, followed by tree plantations, while old-growth forest is confined to only a few locations, contradicting government reports on the area of the district under forest cover. The study contested the India State of Forest (ISFR) 2015 report that claimed a total of 79 percent (78.84 percent) ‘forest cover’ in West Garo Hills district. Authors had told Mongabay-India that without a revision of the definition of forest, the map classes, and mapping methodology, claims about shifting cultivation-induced deforestation cannot be made.
REDD++ in shifting cultivation landscapes for conservation
Despite the ambiguity in government nomenclature and forest mapping, successful implementation of carbon-based payment for ecosystem services (PES) schemes, such as REDD++ (Reducing Emissions from Deforestation and Forest Degradation), can also conserve biodiversity in shifting cultivation landscapes by protecting its habitats.
Borah’s research shows a “strong potential of REDD+ in protecting landscape-level carbon stocks.”
“Our assessment of potential management strategies under REDD+ suggests that sparing old-growth forests from conversion into shifting cultivation by intensifying cropping in a smaller area is the most optimal strategy for protecting landscape carbon. In the existing shifting cultivation system without any old-growth forest, REDD+ funding can be invested in sparing older fallows, which also stores a significant amount of landscape carbon, for permanent forest regeneration,” she said.
Maintaining a longer fallow cycle, for instance at a 15-year cultivation cycle can also sequester considerable levels of carbon compared to landscapes with short fallow cycles (5- and 10-year cultivation cycles).
“The results from my overall Ph.D. work reveal that shifting cultivation maintains high levels of carbon stocks and bird diversity, suggesting potential win-win outcomes for conservation interventions. Particularly, mosaic landscapes with farmland and regenerating secondary forests in Nagaland sustained high levels of bird diversity including forest associated species of conservation concern. This implies the high conservation value of shifting cultivation landscapes in storing carbon and sustaining species diversity,” she said.
However, caution must be exercised while framing REDD+ projects in the context of shifting cultivation landscapes so as to not increase farmers’ vulnerability. Some of the issues that need careful consideration are reliable carbon and biodiversity monitoring protocols, safeguards to avoid leakage, addressing tenure insecurity, and efficient coordination across various stakeholders.
“The indigenous communities in shifting cultivation landscapes depend heavily on forest resources for their livelihood and play an important role in forest protection and management. The REDD+ mechanism, if not designed carefully, could potentially increase the vulnerability of these farmers to negative socio-economic changes. With the careful introduction of REDD+ while accounting for the cultural diversity and societal inequalities, there is a strong potential for major carbon and biodiversity benefits in shifting cultivation,” elaborated Borah.
One example of a REDD+ project that could be replicated is the Khasi Hills Community REDD+ project, which aimed to protect sacred groves and watersheds and replant degraded land. It was India’s first community-based REDD+ project and employed members to monitor forests and complete carbon assessments.
Banner image: Angami Naga tribe innovated the Alder coppicing system by retaining and pollarding nitrogen fixing Alder trees that facilitate fallow regrowth in Khonoma village, Nagaland. Photo by Joli R. Borah.
CITATION: Thong, P., Sahoo, U. K., Thangjam, U., & Pebam, R. (2020). Pattern of forest recovery and carbon stock following shifting cultivation in Manipur, North-East India. PloS one, 15(10), e0239906.
Borah, J. R., Evans, K. L., & Edwards, D. P. (2018). Quantifying carbon stocks in shifting cultivation landscapes under divergent management scenarios relevant to REDD+. Ecological Applications, 28(6), 1581-1593.