Framed in the lens of my binoculars is a tiny bird clinging to the reeds. For a moment, my entire attention is captured by the vivid flashes of yellow and white as the bird flits between the grasses. The surrounding backdrop of untidy skyscrapers disappears, and I am alone in a watery tapestry of bulrushes, fluttering dragonflies, and trilling birds. But the mellifluous calls of the Yellow-bellied Prinia (Prinia flaviventris) soon fade away, the pungent smell of sewage assails my nostrils, and I am bombarded with the sounds of traffic, the honking of horns, and the city once again impinges on my consciousness. I am in the Okhla bird sanctuary, situated in the heart of Delhi close to the Noida expressway, and I cannot help but marvel at the enormous biodiversity of this city that keeps throwing up new surprises every year-reports of a vagrant Smew or the Baikal teal making brief forays into this polluted city and its environs, even as the concrete jungle continues to gobble up surrounding peri-urban lands.
But cities can and do sustain considerable biodiversity and extensive green areas. With cities holding more than half of the world's population, the reality is that for many people the only biodiversity they will ever see is in their backyards. Urban green areas are now being viewed as an essential component of city planning that provide a myriad of ecosystem services to the people and wildlife that live in urban spaces. Green spaces play a multitude of roles; as ways to regulate the climate, to trap pollutants, as noise breaks, as refuges for wildlife and plants, including endangered species and for educational or recreational purposes. Psychological and physical wellbeing is often intimately tied to the presence of natural areas. Many cities across the world now maintain significant proportions of their area under urban green spaces ranging from 20-30% of the area of the city, and accounting for 15 to 25 m2 of green space per capita. The World Health Organization provides guidelines on the minimum available green space per person, and suggests that each individual should have at least 9 m2 of green space although developed countries often use a higher yardstick of 20 m2 park area per city dweller.
A purple sunbird in a city garden.
Biodiversity concerns are increasingly being integrated into urban planning. Current information on ways to integrate biodiversity within city planning, however, remain scarce, but we need to actively plan for conserving wildlands by integrating them with human society, through what Daniel Janzen, an influential tropical biologist calls the 'gardenification of wildland nature.' Grimm and others writing in the journal Science in 2008 mention that given that increasing fractions of people who live in or around cities, "these are the biological communities that humans experience-human connections and encounters with urban nature have supplanted experiences with natural biodiversity." Ideally, therefore, these biological communities need to be made as diverse and as similar to wild nature as possible, ensuring the many ecosystem services that green spaces provide. Increasingly, the design of urban centres and cities are beginning to resemble ecological networks consisting of connected green patches that avoid fragmentation, protect nature and integrate the city with its native biodiversity.
Some Indian cities sustain amongst the highest biodiversity in the world, although in general data is lacking on the extent of urban forests or biodiversity of Indian cities. According to the Forest Survey of India (2013), urban forests account for 12.12 % of the geographical area of Delhi leading to approximately 10.7 m2 per inhabitant (using population data of 2011). In Chandigarh, the average forest cover is 15.14% of the area or about 16.3 m2 per person. Although the density of trees in Bangalore is lower than many other Asian cities, the species diversity is very high. Other cities like Jaipur have far lower forest to people ratios.
An isabelline shrike in the Basai fields.
In several Indian cities, wildlife survives amidst skyscrapers and burgeoning human populations. Delhi city and the surrounding areas of the National Capital Region (NCR) with more than 400 bird species, has the distinction of hosting the second highest number of bird species of any city in the world apart from Nairobi! And the bird list keeps getting longer every year as enthusiastic groups of birdwatchers and photographers keep recording the presence of new species within the bustling metropolis. Mumbai has the Sanjay Gandhi National Park. Coastal cities harbor mangrove ecosystems and much marine life; Chennai for example has nesting sites for the Olive Ridley's turtle. Pune and Bangalore harbor several species of amphibians.
There may be many reasons for the high biodiversity of some cities-their location in transitional biogeographic zones, proximity to forested areas such as the Western Ghats-e.g. Pune, the existence of sanctuaries and national parks within or close to their boundaries, their location along important avian flyways and the presence of natural or man-made wetlands and rivers that attract thousands of migratory waterfowl every year. Maintenance of a mosaic of natural or semi-natural ecosystems such as wetlands, forests, riverine areas, agricultural fields and grasslands, ensure the representation of a number of species illustrative of different habitat types. Cultural and religious reasons may also help conserve wildlife in cities, given the intimate connection of many Indian religions over the centuries with wild fauna and flora.
The forests in and around Delhi support significant wildlife including the nilgai (Boselaphus tragocamelus), jungle cat (Felis chaus) and jackals (Canis aureus) (personal observation), as do areas adjoining the city of Pune probably due to the surrounding hill forests. Shasrabuddhe in 2009 reported that as many as 60% of the butterfly species of Pune are believed to feed on host plants located in these hill forests. Maintenance of corridors that facilitate dispersal of fauna and flora and prevent the fragmentation of important ecosystems is often critical to the maintenance of a city's biodiversity. At the same time preservation of wild areas located in the vicinity of cities (such as Mangar Bani, a sacred grove in Gurgaon for example) is important, both as source populations for cities as well as in their own right as refuges of native flora and fauna. The presence of a diversity of habitats and species can also bring in significant tourism revenues for a city's residents, as is amply evidenced by the sight of binocular-toting tourists visiting Sultanpur National Park or Okhla in the winter, hoping for a glimpse of delicate pink and white-hued flamingos or whatever rarity these areas have thrown up that year.
The biodiversity of cities, however, face extensive threats, loss of habitats to reclamation or urban development, road kills, straying of animals into city centres or even hunting and poaching. City frontiers expand inexorably into surrounding rural and wilderness landscapes causing extensive changes to forests, wilderness, agriculture and other fringe ecosystems. The Basai wetlands on the outskirts of Delhi, for example, consisting of inundated agricultural fields once teeming with thousands of migratory waterfowl such as greylag (Anser anser) and bar-headed (Anser indicus) geese or Northern lapwings (Vanellus vanellus) in abundance, a virtual Mecca for all birders visiting Delhi, have now been sold for housing development. In Pune, urban sprawl has increased over the years primarily at the cost of agriculture and grassland-scrub. In the past, a single monsoon shower in Delhi would inevitably be accompanied by a chorus of croaks as amphibians emerged in search of mates-today it is the silence that is deafening. Lack of knowledge is another threat-I have come across numerous instances of people slaughtering monitor lizards (and of course snakes) wrongly believing them to be venomous.
Conversion of primary or secondary forested regions or other wilderness areas within cities can lead to the local extinction of species. Even if these forested habitats are converted to 'horticultured' parks and gardens, thus technically maintaining green areas, the loss of important wildlife habitats can have detrimental consequences for many habitat specialists. At the same time, a city with a high density of native, mature trees by providing appropriate nest holes and much structural diversity can have high abundances of some species of fauna. Delhi, for example with its many tall trees of high diameter appears to attract higher abundances of birds like hornbills and yellow-footed green pigeons than many nearby villages increasingly devoid of any mature trees.
Wetlands that provide numerous services; fish, ground water recharge, aesthetic values, biodiversity and tourism opportunities- are particularly prone to drainage and destruction. The Okhla bird sanctuary on the river Yamuna in Delhi is an example of an extremely important site for breeding and over-wintering waterfowl which in a good year attracts thousands of waterbirds in the winter including endangered and vulnerable species like the Baer's Pochard (Aythya baeri) and other birds like the Indian Skimmer (Rynchops albicollis) and Bristled Grassbird (Chaetornis striatus). In winter 2010, a Baikal teal (Anas formosa) was reported from this area. However, the sanctuary is increasingly under threat due to urban development occurring in its immediate vicinity. Nevertheless, wetlands are increasingly being valued for the important ecosystem services they provide. Examples of urban managed wetlands are the East Kolkata wetlands that represent the largest assemblage of sewage-fed fisheries in the world. These wetlands provide food and livelihood security to 0.2million of the poorest peri-urban populations and provide up to 80% of the fish and 60% of the agriculture to the city of Kolkata. These wetlands are now considered to be an integral part of the urban infrastructure and an East Kolkata Wetland Authority has been set up for their conservation and management.
Elusive sightings of the migrant Baikal teal, in Okhla in 2010 after a span of 40 years and then again in Sultanpur in 2013.
Citizens can play a key role in monitoring and recording the presence of important wildlife species that often provide an important indication of the ecological health of a city, both for its human and non-human inhabitants. The UK is a prime example of how amateur birdwatchers and citizens have carried out pioneering work in organizing bird censuses, bird ringing programmes and the development of detailed atlases documenting bird distributions. For example, trends shown by the Common Birds census in the UK carried out by citizens provided solid evidence of the decrease in farmland birds in the UK and motivated the British government to uses an index of farmland birds as an indicator of 'Quality of Life'. Similar initiatives are beginning in India such as Migrant Watch, and increasingly citizens of cities such as Delhi are monitoring the decrease of birds such as the once ubiquitous house sparrow. A local birding group of Delhi conducts an annual 'Big Birding Day', where the numbers of bird species seen from dawn to dusk are recorded. Citizens are regenerating a 240 ha tract of the Aravalli range formerly used for mining in Gurgaon with native species of trees involving seed collections from across India.
This Aravalli Biodiversity Park as it is called, now provides an ideal scrubby, habitat for White-eared Bulbuls (Pycnonotus leucotis), Yellow-eyed Babblers (Chrysomma sinense), the red-lipped Sirkeer Malkoha (Phaenicophaeus leschenaultii), and even for civet cats and reptiles like the monitor lizard (Varanus bengalensis).
The importance of developing metrics for monitoring and protecting urban biodiversity has not gone unnoticed by the global community. The ninth meeting of the Conference of Parties to the Convention on Biological Diversity recognized the role of cities and local authorities in the implementation of biodiversity strategy and action plans. This led to the creation of an index to measure biodiversity in cities known as the City Biodiversity Index. India has already indexed the biodiversity of Hyderabad, but it is high time that other cities follow suit. And once cities start competing for high ranks on this index, each puddle in the monsoon, each fruiting tree that attracts 'frugivores' like barbets and hornbills, and each untidy backyard planted with native, flowering herbs and shrubs, and covered with leaf litter for frogs, will, one hopes, acquire invaluable meaning for urban wildlife and their city protectors.
Pia Sethi has a PhD in ecology from the University of Illinois, and is currently a Research Fellow in the Forestry and Biodiversity Group of TERI.