BHARAT SHARMA ACHARYA
Climate change is unambiguous for many, including climate pundits and policy makers, while a myth to some skeptics. These stratums are strong on the ground of their ponderings. Despite the debate, the current unprecedented increase of greenhouse gases is what can’t be neglected. According to the Intergovernmental Panel on Climate Change 2007, carbon dioxide has accelerated from pre-industrial value of 280 to 380 parts per million in 2005, and is expected to grow. The sheer necessity of present climate crisis is mitigation strategies for greenhouse gases (GHGs).
Climate mitigation strategies include reduction, offsetting and avoiding the emission of green house gases. Carbon repositories like forest or grassland are, therefore, crucial in reducing greenhouse gases emission and increasing resilience of ecosystem to adapt to changing climate. Grasslands can be exploited as potential sink to reduce atmospheric greenhouse gases.
Grasslands account for 27% of the total land area of Nepal together with shrub lands and savannas, according to Earth Trends, 2003. The importance of grasslands is entrenched in a range of ecosystem service. Grasslands provide habitat for a wide range of species, including endangered animals and migratory birds, fodder for livestock production, and cane and thatch for buildings to rural communities. The 7th Conference of Parties in Marrakkesh allows the inclusion of grazing land management as a mechanism to account and reduce anthropogenic emissions of greenhouse gases.
Grass harnesses the carbon released into atmosphere from industries and power plants, and incorporate it into their biomass which ends up into soil as soil organic matter. This carbon capture and storage is basically called as carbon sequestration. Carbon sequestration in grassland is rather cheap and technically feasible strategy of emission reduction. Neither do we need to install any equipment nor do we need to work exhaustively. The underlying principle to enhance soil carbon sequestration is to put more carbon input like roots, foliage or litter into the soil, whilst slowing down the decomposition rates of soil organic matter. Decomposition of soil organic matter by micro-organisms and soil fauna is critical because they have a propensity to release carbon dioxide gases back into the atmosphere. It has been reported that carbon sequestration in permanent pasture can potentially offset 4% of global greenhouse gas emission.
The management of grasslands is crucial to increase resilience of the ecosystem. Management options purposed to enhance carbon sequestration include fertilization, irrigation, inter-sowing of grass and legumes, introduction of deep-rooted species, conservation tillage, and crop rotation. Intensively managed and fertilized grassland is reported to hold higher carbon than less managed grasslands.
Grazing is an inseparable aspect of grasslands, and can stimulate tiller production, and cycling of carbon and nitrogen through incorporation of foliage and animal excreta. However, heavy traffic and overgrazing may reduce carbon stocks.
Grasslands in Nepal are either poorly managed or degraded. Many grassland habitats are threatened by invasion of woody plant species. Management commonly followed includes annual cutting and burning. They are deemed important in preventing succession of grasslands into forest, and hot burns during dry periods of the year. Taking an account of the amount of grass that go into the soil as carbon input after the cutting is fundamental for carbon sequestration. Fires are often considered devastating because they upshoot huge emissions of greenhouse gases.
Livestock grazing and stocking rate in rangelands of Nepal has been reported several times higher than their actual carrying capacity. In agricultural systems, cultivated grasslands exist where crop rotation is practiced. Cultivated grasslands, in many parts of the country, are frequently tilled ensuing huge loss of carbon through decomposition of soil organic matter. Moreover, transition of many natural types of grasslands into agricultural lands or concrete jungles have depleted antecedent carbon repositories; these all offer a range of carbon sequestration possibilities. There is an acute need for sustainable development, conservation and management of grasslands biome, but challenges still remain. It is necessary to develop policies that aim to provide economic incentives to farmers maintaining and managing cultivated grasslands. The state should prioritize the development of community grasslands, which enables people to manage and conserve their carbon sinks.
The studies on carbon storage potential of natural and cultivated grasslands of Nepal are limited. Long-term monitoring of soil carbon is necessary for scaling-up carbon sink capacities of different grasslands. Owing to huge potential of grasslands for mitigation of GHGs, we all need to act collaboratively with immaculate timing.
Acharya is conducting research on Carbon Sequestration in Denmark