Current Research

The spatial and temporal domains of modern ecology, published in Nature Ecology and Evolutionis a new study led by collaborator Lyndon Estes that endeavors to reveal the observational extents of studies across the discipline of ecology, in both space and time. We find that while ecologists have made some advances in studying larger extents and finer resolutions, there are still significant gaps in what we observe and describe. Most observations are at resolutions of less than one square meter and with extents less than 10,000 ha. Ecologists also tend to make repeat observations infrequently and study processes for less than a year. Technologies, such as remote sensing and unmanned aerial vehicles, can pave the way for expanding observational extents and drilling down to finer resolutions, while also potentially doing so at more frequent intervals. Filling in the observation gaps can help ecologists understand more about the processes they aim to study.


The observational domains of modern ecology

Check out a related News and Views article that further highlights some of the important findings, as well as a blog post written by Lyndon Estes and Tim Treuer, describing the ideas that led to the study, and the process of reviewing and scoring hundreds of academic papers to uncover the scales of ecological observations.

New paper in Proceedings of the Royal Society B on determining how the influence of temperature and competition on bird community structure varies across seasonality and species richness gradients in the Himalayas. We surveyed bird communities during breeding and winter along opposing seasonality and bird species richness gradients in two regions of the Himalayas separated by 1500 km. We deployed temperature loggers to link each bird observation with temperature, and used this to create season-specific thermal niches for 120 bird species. This enabled us to look at the degree to which species track temperatures across seasons (a measure of the abiotic influence) and to look at the degree to which potentially competing species segregate in thermal space (a measure of the biotic influence).

Species in less seasonal environments were more constrained by temperature than species in seasonal environments, suggesting they may be more sensitive to further changes in temperature. Surprisingly, we found that seasonality influenced the strength of competition in both regions, but in context specific ways. Competition was intensified during winter in the more seasonal environment across species; in the less seasonal environment during winter, competition intensified between species with similar ecologies (measured by body size). Our results demonstrate that abiotic and biotic factors interact to structure bird elevational ranges and entire communities, and point to both heightened thermal sensitivity and enhanced competition playing particularly important roles in structuring ecological communities in tropical regions.



New paper featured on the cover of Indian Birds – read a new paper in Indian Birds describing the distribution of White-browed Shortwing in the western Himalayas, lead by Gunjan Arora. The White-browed Shortwing has a disjunct range, with very few records west of Nepal. I observed and recorded the song of this species in Sarmoli village near Munsiyari, Uttarakhand in May 2014, one of only a few records in the state.



Research featured on the cover of the February 2017 issue of Ecology

Caption: Mixed coniferous forest at 2900 m in Great Himalayan National Park, India, in December 2012. Stark habitat transitions, such as those between mixed coniferous forest (foreground) and upper temperate forest (seen in background), limit the elevational distributions of many Himalayan birds, but temperature dominates as the primary range-limiting factor. See Elsen et al. in this issue (doi: 10.1002/ecy.1669). Photo credit: Paul R. Elsen

Disentangling the factors limiting species distributions

A fundamental yet unresolved question in ecology is why species occur where they do, and not elsewhere. I explore this question utilizing unique natural climatic and species richness gradients in the Himalayas. Through fieldwork and abundance modeling, my research attempts to disentangle three leading hypotheses – climate, habitat, and

Treeline above mixed Rhododendron and upper temperate forests, Uttarakhand, western Himalayas

competition – thought to limit bird elevational ranges. Results from this work have revealed surprising differences in Himalayan bird communities compared to previous foundational work in the tropics. Whereas the majority of tropical bird species are thought to be primarily limited by competitive interactions, the majority of birds from the temperate Himalayas are primarily limited by temperature. These results suggest that contrasting mechanisms may be limiting species across latitudinal gradients. Furthermore, my findings underscore a significant sensitivity of Himalayan birds to temperature that suggests their distributions may be substantially influenced by ongoing climate change.

Related Publications:

Elsen, P. R., Tingley, M. W., Kalyanaraman, R., Ramesh, K. & Wilcove, D. S. 2017. The role of competition, ecotones, and temperature in the elevational distribution of Himalayan birds. Ecology 98, 337-348. Link PDF

See media and news related to this work:

Princeton University Press Release



Determining the impacts of agriculture and grazing on Himalayan birds

The Himalayas are a global biodiversity hotspot containing nearly 10% of the world’s birds. At the same time, the region has undergone rapid deforestation, largely driven by the expansion and intensification of agriculture and grazing. My research attempts to understand how the conversion of natural forests to agriculture impacts Himalayan bird communities in terms of abundance, species richness, and community composition, as well as understand the ultimate drivers of species loss. My results from fieldwork studying bird communities across a gradient of agricultural intensity suggest that low intensity ag lands (consisting of small-scale subsistence agriculture within a matrix of lightly used forest) as well as medium intensity at lands (consisting of mixed terraced agriculture)

Terraced mixed agriculture in Himachal Pradesh, western Himalayas

harbor significantly greater abundance and bird species richness than high intensity ag lands (heavily grazed pastures), but also greater than primary forest. Surprisingly, this finding was true both during winter, when forest resources are scarce and birds migrate to lower elevations into human-dominated landscapes, as well as during summer, when species are breeding. However, primary forests harbored unique species during both seasons, and had a distinct community composition compared to agricultural lands. Furthermore, intensifying agriculture through heavy grazing significantly reduced both abundance and bird species richness, and led to homogenized communities. My results suggest that low intensity agricultural lands are important for the majority of Himalayan birds throughout their annual cycle. Conservation strategies in the Himalayas must therefore go beyond establishing protected areas and prioritize retention of low intensity agricultural lands, minimizing their intensification, given their relatively high conservation importance for Himalayan birds.

Related Publications:

Elsen, P. R., Kalyanaraman, R., Ramesh, K. & Wilcove, D. S. 2017. The importance of agricultural lands for Himalayan birds in winter. Conservation Biology 31, 416-426. Link PDF

See media and news related to this work:

Blog article summarizing research by Fred Singer

India Water Portal (in Hindi)

CatchNews (in Hindi)


Developing priorities for montane species conservation

Montane species are expected to be particularly threatened by climate change as warming temperatures drive species’ ranges upslope. This is based in part on the assumption that species are squeezed into ever-smaller areas as they ascend, leading to population declines and eventual extinction. I conducted a global analysis of topography to illustrate that a diversity of area-elevation patterns exists within the world’s mountain ranges, which suggests that population responses will be specific to their local,

Complex topography beyond Great Himalayan National Park, Himachal Pradesh, western Himalayas

topographic context. Accounting for underlying topography in conservation planning can therefore target critical “pinch points” where species’ range shifts result in significant area reductions. Protection of these key “topographic corridors” may facilitate species adaptation to climate change. Within this theoretical framework, for my current Smith Fellowship I am developing and implementing a novel approach to conserving montane species under climate change across US mountain ranges, with particular focus on California ranges. Results will identify both priority regions for montane conservation and context-specific recommendations for stakeholders to guide climate-informed, proactive conservation strategies for species adaptation under climate change.

Related Publications:

Elsen, P. R. & Tingley, M. W. 2015. Global mountain topography and the fate of montane species under climate change. Nature Climate Change 5, 772-776. Link PDF

See media and news related to this work:

Washington Post


Carbon Brief

Atlas Obscura

MinutePhysics Video