The harsh biogeography of the Trans-Himalayan Plateau supports a unique high-elevation rangeland in Eastern Ladakh. These tablelands have characteristic vegetation assemblages forming alpine rangelands that have supported nomadic pastoralist communities co-existing with inimitable wildlife across millennia. The topographic and climatic restraints have sculpted a distinctive grassland ecosystem that although low in biomass and ecological productivity supports a host of native floral and faunal diversity. However, livestock overgrazing is signficantly threatening the rich biodiversity of the region.
The resident communities have practised traditional pastoralism rearing different livestock on these pastures to sustain their livelihood, a key component of which is the production of the finest cashmere Pashmina wool in the world. In recent decades, a gradual shift in socioeconomy has increased grazing pressure on the rangelands.
Along with the looming influence of a changing climate, overgrazing has altered the composition of rangeland vegetation; endangered wildlife through competition; and threatened ecosystem productivity. These trends are projected to have detrimental connotations for sustenance for biodiversity, ecosystem services and herding livelihoods in the alpine rangelands.
What is driving livestock overgrazing?
The pastoral communities resident in the region have undergone a transformative change since the last century. Traditionally, the communities practised a hybrid agro-pastoral livelihood, trading their livestock produce (mainly meat and wool) for salt with Tibetan tribes across the international boundary between Ladakh and Tibet (Now Tibet Autonomous Region, China).
They met their food security by practising subsistence agriculture on small landholdings. However, post the Indo-Sino war of 1962, transboundary trade ended and the region observed an influx of Tibetan Refugees bringing additional livestock and increased grazing pressure in the region.
Furthermore, socio-economic changes such as the introduction of policies providing base food grain availability through subsidies have encouraged people to focus more on grazing-dependent livelihoods. Policies are also aimed at encouraging communities to stay in the remotest parts of the region and dissuade outmigration to partly address growing territorial and geo-political tensions with China.
Simultaneously, there has been a change in aspirations of the communities driven by an increased impetus on cash-based incomes which are mostly met through Pashmina wool production. Pashmina production has been also endorsed directly by the government to foster economic growth by capitalizing on increasing international demands and boosting the export of this high-value commodity.
The Rich Biodiversity of these Rangelands
Despite being a low productivity ecosystem, the rangelands harbour a diverse array of herbaceous diversity which in turn support not only the grazing communities but a plethora of native and endangered faunal diversity such as the Tibetan gazelle, Tibetan Wild Ass, Argali, Snow Leopards, Himalayan Brown Bear, Bharal/Blue Sheep, Tibetan Wolf, Red Fox, Himalayan Lynx and many more.
The aforementioned social changes have increased livestock populations and put tremendous grazing pressure on these fragile rangelands. Coupled with the fact that these rangelands are among the most vulnerable regions to the influences of a rapidly changing climate, several studies predict adverse negative impacts on the vegetation cover, phytosociological composition, dependent wild fauna populations, ecosystem productivity and consequently regional livelihoods security.
How does livestock overgrazing impact vegetation diversity and health?
The vegetative cover across the landscape is broadly of three types, greatest proportion is under desert steppe interspersed by alpine scrub and even marshy meadows! Despite the harsh climate, short growing season, nutrient-poor soil and low rainfall, Ladakh supports considerable floral diversity with some of the earliest studies documenting over 600 vascular plants (plants with differentiated roots and shoots) from 51 families to more recent ones documenting 1085 flowering plants from the region.
Although they may look uniform and carpet-like to the uninformed eye, the grasslands are composed of a variety of sedges, forbs and rushes (different types of grasses based on their stems, leaf blade and root structure). These belong to a plethora of families but majorly Poaceae, Asteraceae, Brassicaceae, and Fabaceae. This is interesting as it is representative of a high monocot-dicot ratio which botanists interpret as a longstanding history of grazing.
Impacts of Elevation on Diversity
A number of regression studies, i.e., studies that analyze the influence of one environmental variable on another, have been conducted to understand the impact of grazing on the species composition across an altitudinal gradient in the region. Due to an undulating topography, height plays a significant role in the pastures accessed by herbivores. Studies suggest that species richness and abundance of several grass species groups is lower at both lower and higher elevations.
This is contrary to the general assumption which hypothesizes that abundance of grass species would be greater at higher elevations as grazing animals would prefer low to medium slopes. However, observations have attributed this phenomenon to the competitive exclusion of palatable grass species by non-palatable species in low-lying areas. Furthermore, at higher elevations weather becomes the more influential factor with temperature sensitive species being outcompeted by cold-tolerant ones.
Standing biomass, which is the dry weight of living organisms (in this case vegetation), is another important measure of rangeland health as it is indicative of the amount of photosynthesis performed by the plant species as well as being a direct measure of the carbon sequestered by them. Overgrazing has been observed to have negative impacts on vegetative biomass with low standing biomass observed at lower elevations because of excessive grazing coupled with subsequent trampling and soil erosion.
Livestock overgrazing can increase plant diversity
However, studies in other parts of Himalaya indicate an increase in species and community diversity under moderate grazing pressure but a decrease under high intensities. There is also contrasting evidence regarding standing biomass under grazing regimes in alpine rangelands with a decrease in biomass observed in Western Himalaya but an increase observed in Eastern Himalaya.
The interrelationships between important ecological indicators such as species diversity and biomass are also crucial in improving our understanding of rangelands health and productivity. Species diversity is widely known to be positively correlated with biomass production in alpine pastures. This is a typical example of the whole being greater than the sum of its parts and is credited to improved ecological niche partitioning.
High grass species diversity means different species perform multifarious roles in rangeland ecosystem and their agglomerative impact on total biomass production is greater. This is due to the differentiated interactions that a complex ecosystem allows, that is, higher diversity facilitates multileveled interactions between species groups such as establishment and regeneration between mutualistic (interactions that are beneficial for both) and commensal (interactions that benefits one and is neutral for the other) species. Such observations reveal the complex interlinkages between grazing patterns and species composition leading to differential impacts on ecosystem functioning and productivity.
Findings from geospatial studies are alarming
Recently, remote sensing based studies on rangeland health assessment using Earth Observation satellites have provided insights on larger spatial (several hundreds of kilometers) and temporal scales (decades). By studying biophysical parameters such as evapotranspiration and concentration of chloroplasts, researchers have drawn relationships between seasonal snow cover melt on grass growth as well as the quantified influence of soil moisture on biomass.
Their findings suggest that climate change has accelerated snow melt in the region and the resultant decrease in duration of standing snow cover has cascading implications for the vegetation health. Alpine meadows have begun blooming earlier and pastoral communities have had to adjust their seasonal herding patterns accordingly. Coinciding with increased footfall from overgrazing, this could have a synergistic detrimental impact on key ecosystem services.
Implications of livestock overgrazing on wildlife
Overgrazing is a coalescent result of changes in livestock holding and grazing patterns; land tenure and socio-economic status of Changpa and Tibetan refugee communities in Ladakh. Sociological studies have revealed a dramatic increase in livestock populations due to changing aspirations; lucrative cash-based income provided by the Pashmina economy; change from polyandry to nuclear families; and erosion of cultural values traditionally sustained by religious institutions.
The resultant grazing pressures are not only detrimental to the vegetation but also to the several endangered species of wild herbivores that are either outcompeted directly by the livestock or left with severely degraded pastures. As herbivore populations plummet, prey-predator relationships are disturbed creating higher incidents of human-wildlife conflicts with carnivores targeting livestock further complicating an already delicate issue.
We must not alienate pastoral communities
Alpine rangelands hold considerable value as a vital source of fodder to herding communities and as vestiges of pristine wildlife habitats along with their wider role as important regulators of carbon flux, soil productivity and climate resilience. Resolving the rising dissidence and conflict of interests between local communities, wildlife bodies and government officials concerning the implementation of environmental laws is paramount for their conservation.
This can only be pursued through a pensive understanding of rangeland ecology and anthropogenic use in tandem with community-based systems of management. Interventions and solutions must involve rigorous consultations with the herding communities. This can only be done by developing trust and respect, especially as the world over ethnic communities are apprehensive of authorities dictating and sometimes taking away their rights over natural resources. The only way forward is to empower them with the necessary scientific awareness, logistical support and financial resources as custodians of the most pristine ecosystems on the planet.
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Written by: Rishabh Srikar