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29 Jan, 2019

To understand and find better ways to enhance the quality of grasslands in Bardia National Park (BNP), NTNC-Bardia Conservation Programme (NTNC-BCP) is conducting a long-term experimental research on grassland ecology. The study is a part of the PhD research of Mr. Shyam Kumar Thapa, Project Chief of NTNC-BCP, who is doing his PhD from Wageningen University, Netherlands. A total of 351 sampling plots have been established in six locations—three in Karnali flood plain and three in Babai valley— where the research aims at addressing an existing issue: how can the quality of grasses in the sub-tropical grasslands of Nepal be improved? 

The experiment predicts that removal of tall grasses by mowing (representing biomass removal by grazing) and nutrient manipulation (representing nutrient input through dung and urine by herbivores) may trigger new growth with higher nutrient content which then may be utilisied by deer thereby trigger the grazing lawn formation process. Furthermore, the experiment predicts that the deer may prefer larger open areas with short nutritious vegetation than areas with tall grasses as an anti-predation behaviour.

Grasslands are spatially heterogeneous areas that consist of a complex mosaic of patches with nutrient rich and poor grasses. Quality of grasses in terms of nutrient and digestible energy content in grasslands decreases along with age and biomass, hence, forage availability is inversely related to grass quality. Large body-sized herbivores (e.g. gaur, rhinoceros, elephant) can consume higher fiber content tall grasses, whereas, small and medium body sized herbivores (e.g., deer) select short grasses with lower fiber content. In the absence of large body-sized herbivores, grasses reach its maturity which are not suitable for small and medium body-sized herbivores. However, when aboveground biomass of tall and matured grasses are removed either through mowing or fire, the fresh re-growth with higher nutrient content are heavily utilised by the small and medium body sized herbivores. 

Improving the quality of grasslands, that is nutrients, will be integral to Nepal's efforts to successfully doubling it tiger population in Nepal by 2022. This is because ensuring healthy tiger populations must necessarily link to healthy prey populations (especially deer), which in turn depend on healthy and suitable grassland habitats. Currently biomass of the plots above the ground have been removed manually by cutting grasses from the plot. Vegetation assessment work is being carried out to see the vegetation composition in the experimental plots.  

The most recent National Tiger Survey in 2018 has posited for 235 tigers in the wild, in comparison to 198 tiger in 2013, and 121 tigers in 2009. This increasing trend is reflected in the tiger numbers in BNP, with 87 tigers in the most recent survey, a very healthy increase compared to the past—50 tigers in 2013, and 18 tigers in 2009. Thus, if the growing tiger population in Bardia is to be maintained, it evidently points to the need for establishing a healthier prey-base capacity, which is only possible if a system of healthy grasslands are in place. This is all the more so, especially since other tiger prey species once prominent in Bardia National Park, such as the nilgai and blackbuck, are nearing extinction, caused very likely by the regeneration of tall grasses, woody shrubs and colonisation by invasive weeds, all of which are hostile to preferred grazing conditions for small to medium sized herbivores.

Author Credits
Mr. Shyam K. Thapa, Project Chief, Bardia Conservation Programme