Asola Bhatti Sanctuary in Crisis: Why Invasive Vilayati Kikar (Prosopis Juliflora) Covers 63.48% of Delhi's Only Wildlife Sanctuary – Explained

Location and Geography: The Asola Bhatti Wildlife Sanctuary (ABWS) is the only wildlife sanctuary in the National Capital Territory of Delhi. It lies on the Southern Delhi Ridge, which is the northernmost extension of the Aravalli hill range. The sanctuary spans approximately 32.71 square kilometres along the Delhi-Haryana border and extends into the Faridabad and Gurugram districts of Haryana.

Historical Background: The Bhatti area, from which the sanctuary derives its name, was the site of large-scale stone quarrying until mining was banned in the late 1980s due to severe environmental degradation. Following the landmark Supreme Court judgment in M.C. Mehta v. Union of India on Aravalli mining, the area underwent restoration. It was notified as a wildlife sanctuary between 1986 and 1991 under the Wildlife (Protection) Act, 1972, consolidating the Asola, Shapur and Bhatti ranges of the Delhi Ridge.

Ecological Significance: The sanctuary represents the last remaining stretch of the tropical thorn forest ecosystem typical of the northern Aravallis. It forms part of the Sariska–Delhi Wildlife Corridor, which connects the Sariska Tiger Reserve in Rajasthan to the Delhi Ridge, allowing movement of species like the Indian leopard. It is also a key habitat in the Northern Aravalli Leopard Wildlife Corridor and acts as Delhi's "green lung", helping in groundwater recharge, air quality regulation and resistance to desertification of the National Capital Region (NCR).

Biodiversity: Native flora include Dhau (Anogeissus Pendula), Ronjh (Acacia Leucophloea), Kikar (Acacia Nilotica), Salai, Palash (Butea Monosperma), Khejri (Prosopis Cineraria) and Ber. Faunal diversity includes Indian leopards, striped hyenas, golden jackals, nilgai, civets, jungle cats, Indian crested porcupines, mongooses, peafowl, snakes and monitor lizards.

Origin and Identity: Prosopis Juliflora is a thorny shrub or small tree (1–12 metres) of the Fabaceae (legume) family. It is native to the arid and semi-arid regions of North America (southwest United States and northwest Mexico), parts of South America and the Caribbean. In India it is commonly called Vilayati Kikar (foreign Kikar), Vilayati Babool or Angreji Kikar — terms that emphasise its foreign origin in distinction to the native Khejri (Prosopis Cineraria).

Introduction to India: The species was introduced into India during the colonial period, primarily in the late 19th and early 20th century, by the British administration to provide quick green cover on degraded land, supply fuelwood, combat desertification and stabilise the Delhi Ridge. Records of the Delhi Forest Department confirm its planting on the Ridge for afforestation purposes.

Why it is Invasive: It is listed by the International Union for Conservation of Nature (IUCN) among the world's 100 worst invasive alien species. Its invasive nature stems from several biological and ecological traits — it tolerates extreme drought, salinity and high temperatures; it has extensive seed production with dispersal aided by livestock (endozoochory — seeds spread through animal dung); it produces dense canopies that suppress sunlight reaching native plants; and it releases allelopathic chemicals through its leaf litter that inhibit germination and growth of native vegetation.

Ecological Impacts: Prosopis Juliflora alters soil chemistry, depletes groundwater (it is a phreatophyte — a deep-rooted plant that taps the water table), creates monocultures, reduces native plant diversity, modifies habitat structure for wildlife and affects pastoralism by replacing fodder species. While its dense canopy currently helps stabilise soil on the Aravalli slopes and serves as a sub-optimal habitat for some wildlife, the WII plan has flagged it as a major ecological threat requiring phased removal.

Phased Invasive Species Removal: The plan recommends a gradual, phased reduction of Prosopis Juliflora rather than abrupt large-scale clearance. This is because sudden removal could expose soil to erosion, harm the species that currently use it as a shelter and trigger ecological imbalance. Phased removal allows restoration to proceed in steps.

Assisted Natural Regeneration: This is a restoration technique where natural regrowth of native vegetation is encouraged through interventions such as removing invasives, protecting saplings, controlling grazing and providing soil moisture support. It is more cost-effective than full plantation drives.

Drought-tolerant Native Plantation: The plan suggests planting indigenous species that are naturally adapted to the semi-arid Aravalli climate — including Vetiver, Munja, Dhau, Palash, Gum Acacia, Salai, Babul, Indigo, Sesban and Siris. These are soil-binding species that prevent erosion, nitrogen-fixing species that enrich soil fertility, and site-specific species that match local ecological conditions.

Soil Moisture Retention Structures: Construction of check dams, contour trenches and recharge pits on ridge slopes to retain rainwater, support root systems of native plants and combat desertification.

Continuous Ecological Monitoring: Periodic land-use change detection through remote sensing, vegetation classification using satellite imagery (Landsat-8), and faunal surveys using systematic camera trapping and line-transect methods.

Animal Management Reforms: The plan calls for proper Standard Operating Procedures (SOPs) for handling translocated wildlife, improved staff training, better rescue and release infrastructure, and monitoring of released animals — particularly Rhesus Macaques.

Delhi has long faced a human-monkey conflict in urban areas. As per the Wildlife Protection Act, the Municipal Corporation of Delhi (MCD) and forest authorities have been capturing nuisance Rhesus Macaques from city neighborhoods and relocating them to Asola Bhatti. Nearly 20,000 macaques have been translocated over the years, but the sanctuary's tropical thorn forest ecosystem cannot naturally support such a large primate population. This has forced the forest department to provide artificial feeding at 18 designated points at a cost of approximately Rs 1 crore per year. This artificial feeding raises ecological and ethical concerns — it disturbs natural foraging behaviour, creates dependency, increases disease transmission risk and pressures other species.

Definition under CBD: The Convention on Biological Diversity (CBD) defines invasive alien species as species whose introduction and/or spread outside their natural past or present distribution threatens biological diversity. The CBD applies an ecological approach — a species can be alien even if it is native to one part of a country but introduced to another.

Definition under Indian law: The Wildlife (Protection) Amendment Act, 2022 inserted Section 2(16A) defining "invasive alien species" as a species of animal or plant which is not native to India and whose introduction or spread may threaten or adversely impact wildlife or its habitat. This is a geopolitical definition — narrower than the CBD's, since it excludes species native to one part of India but invasive in another (for example, Prosopis Cineraria introduced outside its natural range, or invasive native plants in the Western Ghats).

Powers under the Amended Act: The Central Government may regulate or prohibit the import, trade, possession or proliferation of invasive alien species; the Chief Wildlife Warden may direct seizure and disposal; and management plans for sanctuaries may include invasive species control.

Examples of IAS in India: Plants — Prosopis Juliflora, Lantana Camara, Water Hyacinth (Eichhornia Crassipes), Parthenium Hysterophorus (Congress Grass), Mikania Micrantha, Mimosa Diplotricha. Animals — African Catfish, Nile Tilapia, Red-bellied Piranha, Alligator Gar, Red-eared Slider, Common Myna (in some regions), and the Giant African Snail.

International Framework: Article 8(h) of the CBD obligates parties to prevent the introduction of, control, or eradicate alien species which threaten ecosystems. Target 6 of the Kunming–Montreal Global Biodiversity Framework (2022) aims to reduce the introduction and establishment of priority invasive alien species by at least 50% by 2030. The IUCN's Invasive Species Specialist Group (ISSG) maintains the Global Invasive Species Database. The International Plant Protection Convention (IPPC) and CITES also have related mandates.

National Action Plan: India has a National Action Plan on Invasive Alien Species under the Ministry of Environment, Forest and Climate Change (MoEFCC), focusing on prevention, early detection, rapid response and long-term management.

Geological Background: The Aravalli Range is among the oldest fold mountain systems in the world, formed during the Proterozoic Era (over 1.5 billion years ago) — far older than the Himalayas. Geologically, the Aravallis are part of the Aravalli–Delhi Orogenic Belt and consist of metamorphic and igneous rocks like quartzite, schist, gneiss, marble and granite. Due to extensive weathering and erosion, today they appear as discontinuous low ridges rather than sharp peaks.

Extent: The range stretches approximately 670 km in a south-west to north-east orientation, passing through Gujarat, Rajasthan, Haryana and Delhi. Guru Shikhar on Mount Abu (1,722 m / 5,650 ft) in Rajasthan is its highest peak.

The Delhi Ridge: The Delhi Ridge is the northernmost spur of the Aravalli range. It is divided into four parts — Northern Ridge, Central Ridge, South-Central Ridge and Southern Ridge. The Asola Bhatti Wildlife Sanctuary lies on the Southern Ridge, which is the largest and ecologically richest segment.

Ecological Functions: The Aravallis act as the "Green Wall of India" — a natural barrier preventing the eastward expansion of the Thar Desert into the fertile Indo-Gangetic plain. Their fractured rocks serve as aquifers, recharging groundwater for cities like Delhi, Gurugram and Faridabad. They support seasonal rivers like Banas, Sahibi and Luni. They are a biodiversity habitat for leopards, hyenas, jackals, peafowl and migratory birds. They moderate the local climate and reduce dust storms over the NCR.

Threats: Illegal mining, urban encroachment, deforestation, invasive species like Prosopis Juliflora and Lantana Camara, and quarrying have caused a 32% drop in forest cover in the central Aravallis between 1975 and 2019.

Judicial Intervention: The Supreme Court, in multiple judgments including M.C. Mehta v. Union of India, has banned mining in the Aravallis and pushed for ecological restoration. In November 2025, the Supreme Court delivered a landmark ruling defining the Aravalli range uniformly and adopting a cluster-based definition (hills within 500 metres are grouped as Aravalli Ranges) mapped on Survey of India toposheets, ensuring better enforceability.

The Wildlife Institute of India is an autonomous institution under the Ministry of Environment, Forest and Climate Change (MoEFCC), Government of India. It was established in 1982 and is headquartered at Chandrabani, Dehradun, Uttarakhand. Its mandate covers wildlife research, training, and providing advisory and management plans for protected areas. WII has played a pivotal role in the All India Tiger Estimation, eco-sensitive zone mapping, species recovery plans for the Hangul, Great Indian Bustard, Gharial and Asiatic Lions, and is the regional training hub for the South Asia Wildlife Enforcement Network (SAWEN). The WII operates the Wildlife Forensic and Conservation Genetics Cell, which assists in tackling wildlife crime.

Lantana Camara is a flowering plant native to tropical regions of Central and South America, introduced to India by the British in the early 19th century as an ornamental garden plant. It has since become one of the most aggressive invasive species in India, dominating forest understoreys from the Western Ghats to the Aravallis and even tiger reserves like Bandipur and Corbett. It crowds out native vegetation, alters fire regimes, releases allelopathic chemicals, and reduces fodder availability. Recent ecological work in tiger landscapes has shown that mass removal of Lantana can revive native grasses and improve prey densities.

The plan applies the principles of ecological restoration as defined by the Society for Ecological Restoration — the practice of repairing damaged, degraded or destroyed ecosystems. Key principles applied at Asola Bhatti include: (i) reference ecosystem-based restoration — using the natural Aravalli tropical thorn forest as a template; (ii) succession-led restoration — phased approach allowing natural regrowth; (iii) native species priority; (iv) addressing root causes — encroachment, grazing, pollution; (v) community participation; and (vi) adaptive management — using continuous monitoring to refine interventions.

This aligns with India's commitments under the United Nations Decade on Ecosystem Restoration (2021–2030), the Bonn Challenge (under which India has pledged to restore 26 million hectares of degraded land by 2030), and the Land Degradation Neutrality target under the United Nations Convention to Combat Desertification (UNCCD).