Waning grasslands: a quantitative temporal evaluation of the grassland habitats across human-dominated upper Gangetic Plains, north India

Abstract

Grassland habitats currently face severe anthropogenic exploitations leading to cascading effects on the survival of grassland-dependent biodiversity globally, particularly in non-protected areas. Significant amount of such biodiversity-rich grasslands in India are found outside protected areas but lack quantitative information on their status. We evaluated the current and historical (30 years) status of the grasslands using a combination of intensive field surveys and GIS tools across one of the most fertile, human-dominated region: the upper Gangetic Plains of north India. On-ground mapping and visual classifications revealed 57% decline in grassland habitats between 1985 (418 km2) and 2015 (178km2), mostly driven by conversion to croplands (74% contribution). Radio-telemetry data from the largest endemic cervid swamp deer (n=2) showed grassland-dominated average home range (50% BBMM) size of 1.02 km2. The animals highly preferred these patches (average Ivlevs index- 0.85) and showed the highest temporal continuity (88%) compared to other LULC classes. Camera trapping within the core habitats suggests critical use of these patches as fawning/breeding grounds. Habitat suitability analysis indicates only ~18% of the entire area along the Ganges is suitable for swamp deer. Accurate mapping (86% accuracy) and characterization of four major grass species revealed a total 144.04 km2 vegetation area, dominated by Saccharum sp. (35%). We recommend protection and recovery of these critical grassland patches to maintain dynamic corridors and other appropriate management strategies involving multiple stakeholders to ensure survival of this critical ecosystem. Such evaluations, if spatially expanded, would be critical to restore this rapidly vanishing ecosystem worldwide.

Functional connectivity in northern swamp deer (Rucervus duvaucelii duvaucelii) population across a fragmented, human-dominated landscape along Gangetic Plains of north India: Implications for conservation in non-protected areas

“…Despite such loss of habitats, the seasonal movement behaviour of swamp deer (Martin and Gopal 2015) helps maintaining genetic mixing among these fragmented grassland patches, which has earlier been reported as their breeding grounds (Paul et al 2021). This is also evident from the patterns of very low pairwise FST values (between Zones 1 to 5).…”

“…These results support earlier reports of swamp deer congregations during summer months (to feed on young vegetation in the floodplains) and migrations at the onset of monsoon (Schaaf 1978;Qureshi et al 2004). Further, the sugarcane fields possibly help in movement between stopover sights in certain time of the year (Paul et al 2021), as reported from other studies from India (Wikramanayake et al 2004;Athreya et al 2007Athreya et al , 2013Talukdar and Sinha 2013;Warrier et al 2020). It is however important to realise that these inferences are based on only two collared individual females, and future efforts to radio-tag more animals (including both male and females) from different parts of this landscape could help us to ascertain the main drivers of such seasonal movement events.…”

“…In total, the study area comprised ~ 3173 km 2 of habitat covering both protected (HWLS and JJCR-1677 km 2 area) as well as non-protected (1496 km 2 area) regions. This landscape is one of the most densely populated areas of the entire country (population density of 1164 people/ km 2 compared to national average of 382 people/ km 2 (Cenus of India 2011)) with a mosaic of land use patterns including agricultural fields (76%), waterbodies (7%), forest (6%), grassland (6%), settlement (4%) and scrubland (1%) ( Paul et al 2021). Despite such high human footprint, these habitats retain rich faunal biodiversity including swamp deer (Rucervus duvaucelii duvaucelii), hog deer (Axis porcinus), nilgai (Boselaphus tragocamelus), fishing cat (Prionailurus viverrinus), Wild boar (Sus scrofa) and birds such as sarus crane (Grus antigone), black-necked stork (Ephippiorhynchus asiaticus), lesser adjutant (Leptoptilos javanicus), Pallas's fish eagle (Haliaeetus leucoryphus) and bar-headed goose (Anser indicus) (Bashir et al 2012;Grimmett et al 2013).…”

“…A total of 450,000 iterations and 50,000 burn-in were performed. For the locprior model-based analyses, we stratified the 120 km stretch of Ganges river in the study area into five continuous blocks (each block length ~24 km) based on earlier recorded swamp deer movement patterns in this landscape (Paul et al 2021). The optimal value of K was assessed using the "Evanno" method in STRUCTURE HARVESTER web version (Earl and vonHoldt 2012).The individuals were sorted as "pure" or "admixed" based on 70% ancestry coefficient threshold values (Ashrafzadeh et al 2021).…”

“…While this information has been critical in designating 'Priority Conservation Areas' in this habitat block (Paul et al 2020), appropriate conservation planning would require further detailed assessments of migration routes, inbreeding status and genetic variation of this population. This is important as the Gangetic block swamp deer exhibit seasonal migratory behaviour (Paul et al 2021) and no information on the genetic status and connectivity is available for this landscape so far.…”