At Asola Bhatti, Delhi’s lone wildlife sanctuary, the threat to the forest is also green.
Prepared by the Wildlife Institute of India, a 10-year management plan for Asola Bhatti Wildlife Sanctuary has found that Prosopis Juliflora alone covers 63.48% of the landscape, making the invasive tree one of the biggest ecological pressures on the Aravalli habitat.
An invasive tree is a non-native species that spreads rapidly and causes environmental, economic or health harm, often by disrupting ecosystems and displacing native plants.
The management plan has flagged invasive species, particularly Prosopis Juliflora and Lantana Camara, as major threats to the sanctuary’s ecological recovery. The plan has mentioned invasive species, encroachment, habitat degradation, cattle entry, biotic pressure, pollution and weak monitoring as among the key problems affecting the sanctuary.
The scale of Prosopis Juliflora dominance is stark in Asola Bhatti.
A land use and land cover assessment in the management plan recorded Prosopis Juliflora across 18.41 sq km, accounting for 63.48% of the sanctuary. In comparison, forest plantation accounts for 18.83%, followed by built-up area (14.07%,) rock outcrop (1.55%), Anogeissus Pendula (0.9%), water bodies (0.76%), bare ground (0.28%) and scrub (0.17%).
The latest India State of Forest Report 2023 also lists both Prosopis Juliflora and Lantana Camara among the major invasive species inside Delhi’s Recorded Forest Area.
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“A detailed vegetation assessment carried out between April and June 2024 found Prosopis Juliflora to be the dominant species across all habitat types in Asola Bhatti,” the plan said, adding that while vegetation recovery is evident in many areas, “invasive Prosopis Juliflora and human disturbance remain challenges”.
It has recommended phased reduction of the invasive species, assisted regeneration of native flora, expansion of drought-tolerant plantations and continuous ecological monitoring.
Prosopis Juliflora, a Mexican mesquite known locally as Vilayati Kikar, was introduced during colonial afforestation and created extensive monocultures on the Ridge, according to Delhi Forest department records. Biological invasion by alien species such as Prosopis and Lantana affects groundwater recharge, buffering local weather and combating desertification.
Prosopis is classified as a major ecological threat because it suppresses native flora and alters habitat structure, but its dense canopy currently helps stabilise soil and serves as sub-optimal habitat for some wildlife, as per the Asola Bhatti Management Plan. The plan has, therefore, called for phased and scientific removal, backed by monitoring, along with intensive restoration using native flora.
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The restoration plan has recommended planting soil-binding species, nitrogen-fixing species and site-specific native vegetation. Suggested species included vetiver, munja, dhauk, palash, gum acacia, salai, babul, indigo, sesban and siris.
Apart from invasive species, the plan has flagged the large influx of Rhesus Macaques as another major stress. Nearly 20,000 macaques have been relocated to Asola Bhatti over the years, and as per the plan, the sanctuary’s tropical thorn forest has limited capacity to meet their natural food requirements. As a result, artificial feeding has continued at 18 designated points, costing nearly Rs 1 crore annually.
The plan has called this model ecologically and financially unsustainable. It has said that artificial feeding has disrupted natural foraging behaviour, helped the macaque population grow beyond the sanctuary’s carrying capacity and caused animals to stray into adjoining human habitations. It has recommended scientific population estimation, carrying-capacity assessment, habitat enrichment with native fruit-bearing species, gradual phasing out of artificial feeding and a humane sterilisation programme.
The plan also flagged a major administrative gap in animal management. Under its human-wildlife coexistence problems, it has listed unscientific release of rescued animals, no SOPs for handling animals, inadequate staff capacity in animal handling, inadequate rescue and release infrastructure, and lack of monitoring of released animals and their health.
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Encroachment and settlement pressure have added to the stress. The plan says Bhatti village continues to be a critical encroachment hotspot, while unauthorised colonies such as Sanjay Colony and Sangam Vihar represent some of the most intense forms of urban encroachment on the sanctuary. It describes these areas as dense housing clusters with pucca lanes, permanent structures and continuous population inflow, contributing to habitat fragmentation, human-wildlife conflict and long-term ecological degradation.
Further, the plan noted that peri-urban expansion near Devli and Tughlaqabad has created overlapping pressure on the sanctuary’s periphery. Free-ranging cattle graze inside the reserve and abandoned mining pits are used for garbage and sewage disposal, creating ecological risks, it said.
Stray cattle have emerged as a direct ecological pressure. Camera-trap data has shown that stray cattle accounted for about 15.1% of all mammal detections, making them the second-most abundant mammal group after rhesus macaques. Cows were the most common, followed by buffaloes, pigs and camels.
As per the plan, stray cattle are often present near monkey-feeding points and waterholes, where they compete with native herbivores such as nilgai and chital and reduce water availability for wild animals.
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Other stresses listed in the plan include waste dumping, greywater inflow, poor sanitation in fringe settlements, illegal grazing, fuelwood collection, fire risk, weak research-based management, inadequate staff training and poor inter-agency coordination.
