Plants, herbivores and communities
Rangeland dynamics in the Trans-Himalaya
More than half of the earth’s land surface is comprised of grazing ecosystems, aimed at sustaining populations of large herbivorous mammals, both wild and domestic. However, the goals of conserving wild species are often inconsistent with those of animal husbandry.
More than half of the earth’s land surface is comprised of grazing ecosystems, aimed at sustaining populations of large herbivorous mammals, both wild and domestic. However, the goals of conserving wild species are often inconsistent with those of animal husbandry. There are numerous examples where wild species have declined with the progressive intrusion of domestic ones.
The Trans-Himalayas represent a vast rangeland system where a large fraction of the original native species assemblages continues to survive alongside a diversity of livestock. However, the landscape is punctuated with instances of local extinctions. At a local scale, (e.g. at the scale of individual valleys or catchments), there are many instances where one or more wild species have gone extinct in the recent past. Our previous work has shed light on the mechanisms by which livestock can drive this process. However, a critical question remains to be answered – how does the ecosystem as a whole fare, with a reduced number of species?
For ecosystems that have evolved with a certain assemblage of herbivores and plants, any sudden extinction event can cause imbalances in the co-evolved pathways that the system would normally follow. An ecosystem’s performance is adjudged by the functions it carries out. For instance, among the most familiar attributes are the primary and secondary productivity i.e., the ability to provide food. Other functions include nutrient-cycling that keep soils fertile, hydro-dynamics that run the water cycle and so on. Loss of species can potentially have serious repercussions on ecosystem functions.
So we must ask, what are the consequences of losing native species and replacing them with livestock on ecosystem processes? This is the broad question we have set out to answer in this project.
- Book Chapter2016Richness and size distribution of large herbivores in the HimalayaIn: Asian large herbivore ecology, Ahrestani, F., Sankaran, M. (eds.), Springer.Download
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Species diversity across several taxa ranging from plants to vertebrates is reported to decrease with altitude, or to show a mid-elevation peak in mountain systems. Plant biomass availability for herbivores is similarly expected to decline with altitude as temperature becomes limiting. However, the relationship between herbivore species richness and altitude has not been examined in detail. We show that while the overall regional pattern (gamma-richness) for 25 large-herbivore species (56 % grazers, 44 % browsers/mixed feeders) in the Western Himalayas shows a mid-elevation peak, the species richness of grazers increases nearly monotonically with altitude peaking at 4000–5000 m. Median body mass of herbivores decreased with altitude, suggesting greater suitability of higher elevations for smaller bodied herbivores. We propose that seasonal altitudinal migration patterns, biogeographic influences, increases in the abundance of graminoids, and an increase in plant nutrients with altitude might explain the unusual high grazer species richness at higher altitudes in the Himalayan Mountains.
- Journal Article2014A penny saved is a penny earned: lean season foraging strategy of an alpine ungulateAnimal Behaviour 92, 93-100
- Journal Article2013Globalization of the Cashmere Market and the Decline of Large Mammals in Central AsiaConservation Biology 27, no. 4 (2013): 679-689
- Journal Article2010Why should a grazer browse? Livestock impact on winter resource use by bharal Pseudois nayaur.Oecologia, DOI 10.1007/s00442-009-1467-x.
- Thesis2008Overwintering strategies and demographic response of bharal (Pseudois nayaur) to livestock grazing and removal, in Kibber Wildlife SanctuaryMSc Thesis submitted to Manipal University