Urban biodiversity: an insight into the terrestrial vertebrate diversity of Guwahati, India

This study focuses on the assessment of the terrestrial vertebrate diversity of Guwahati. Twenty-six species of amphibians, 57 species of reptiles, 214 species of birds, and 36 species of mammals were recorded during the study period. Thirty-three species were found to be threatened with extinction and another 62 species need evaluation. A single species of turtle was found to be categorized as Extinct in the Wild under the IUCN Red List of Threatened Species.


INTRODUCTION
It has been estimated that the urban population of developing countries is growing at the rate of five million people per month. Roughly 70% of global population is expected to be urban by 2050, and the total urban area is expected to triple between and 2030(U-Habitat 2013. Recent studies have focussed on the biodiversity of urban areas. A study in Hyderabad documented 1,305 vascular plant species, 30 odonates, 42 spiders, 141 butterflies, 60 fish, 16 amphibians, 41 reptiles, 314 birds and 58 mammal species (Srinivasulu & Srinivasulu 2012). A study at National Environmental Engineering Research Institute campus at Nagpur, Maharashtra recorded 135 vascular plants including 16 monocots and 119 dicots, belonging to 115 genera and 53 families (Gupta et al. 2008). A rapid assessment survey at the campus of Indian Institute of Technology, Madras recorded 298 plant species, 50 butterflies, eight amphibians, 13 reptiles, 51 birds and 12 mammal species (Care Earth 2006). Sudha & Ravindranath (2000) recorded 374 species of plants in Bangalore, where a study of street trees identified 108 species belonging to 33 families (Nagendra & Gopal 2010). A similar study in Delhi found 125 tree species (Bhalla & Bhattacharya 2015). A study in Chennai metropolitan city revealed the presence of 45 species of plants representing 21 families (Muthulingam & Thangavel 2012).
During the past 50 years the population of India has grown 2.5-fold and the urban population five-fold (Taubenböck et al. 2009). Analyses suggest that 8% of terrestrial vertebrate species on the IUCN Red List are imperiled largely because of urban development (McDonald et al. 2008), and 13% of endemics are in ecoregions that are under threat from urban expansion (McDonald et al. 2018). Thus, it is important to take research and conservation efforts regarding urban biodiversity more seriously. In urban landscapes the participation of inhabitants is a must for conservation, where effort must be invested in sensitising the community about the benefits of conserving urban biodiversity. Some of the services provided by urban biodiversity are improvement of air quality and regulation of microclimate by urban parks and vegetation. Tree cover and vegetation also helps in proper percolation of rain water to soil, adding to ground water and reducing floods while improving quality of life by adding aesthetic and recreational value. It has been estimated that a ten percent increase in canopy cover can reduce local temperature by 3 -4 0 C ( Gill et al. 2007;Middel et al. 2015).
Guwahati (26.144 0 N & 91.736 0 E), the capital of Assam, is the biggest urbanized centre of northeastern India. The city falls within the Indo-Burma Biodiversity Hotspot, situated between the southern bank of the Brahmaputra River and the foothills of the Shillong plateau. It is spread over 216.79km 2 area, and has a population of around a million with a density of 2695.43 humans per sq.km. The city is situated on undulating plain with varying altitude of 49.5-55.5 m. The city is surrounded by 18 hills. Guwahati has eight reserve forests (South Kalapahar RF, Fatasil RF, Jalukbari RF, Gotanagar RF, Hengrabari RF, Sarnai Hill RF, Garbhanga RF, Rani RF) and two wildlife sanctuaries (Deepor beel WLS and Amchang WLS) along with an internationally acclaimed wetland and Ramsar Site, the Deepor Beel, within the city limits. Deepor Beel Wildlife Sanctuary (WS) is a part (4.01km 2 ) of the Ramsar site which is 40km 2 in area. The mighty Brahmaputra River flows through the city for about 25km dividing it into northern and southern areas (Devi & Bhattacharyya 2015).
Guwahati has a tropical monsoon climate and receives about 1,600mm annual rainfall with an average annual temperature of 23 0 C. Certain patches of forest still exist within the city (Fig. 1). The overall habitat type in the study area mainly comprises of forest patches, scrublands, grasslands, plantations, wetlands, agricultural lands, human settlements and commercial areas. The forest patches are of moist deciduous type (Purkayastha 2012(Purkayastha , 2015. Due to urbanization and anthropogenic pressure, the biodiversity of the city is under stress. Cutting of hills, illegal felling of trees and degradation of wetlands is having an immense adverse effect on the biodiversity of the city. The hills of the city are used for illegal settlements most of which are reserve forest lands raising serious ecological concern. In the hills within Guwahati Municipal Area, there are 65,894 households of which 10,208 are within reserve forests (Devi & Bhattacharyya 2015). Importantly, a large part of Guwahati has been developed by filling of wetlands and the process of filling and degradation of wetlands still continues. Owing to this, Guwahati is seeing a rise of the artificial flood in the low lying city centers.
Due to factors cited above, an assessment of biodiversity of Guwahati becomes important for the formulation of long-term conservation policies. It is a fact that Guwahati has lost a big chunk of its biodiversity, but quantification of the same is not possible as we do not have data on its biodiversity from the past to compare with the present status of biodiversity. This paper provides an inventory of terrestrial vertebrate

MATERIALS AND METHODS
This study was conducted between the year 2011 and 2016 spanning over a period of six years with survey emphasizing on terrestrial vertebrates. The study site was the Guwahati city (26.1859 0 N, 91.7477 0 E), the biggest metropolis of northeastern India and the economic hub of the region (Fig. 1). Since the main goal of the study was to create a checklist, visual encounter survey (Crump & Scott 1994) employing randomized walk (Lambert 1984) was conducted. Active search (Rolfe & McKenzie 2000) was employed specifically for herpetofaunal survey. For herpetofaunal survey, six man hours were invested per survey, with an approximate of six surveys per month from April to October each year between 2011 and 2016. Most of these surveys were undertaken in the evening and early night which also covered observations on nocturnal birds and mammals. Bird surveys were conducted round the year, with more survey efforts being invested during the winters (November-March). We used Olympus 10X50 DPS binocular for the survey. Twelve man hours were generally invested per survey with most conducted in early morning or evening. Mammal survey was conducted in association with bird survey.
Records of rescued animal with locality details by Assam State Zoo were also taken into account while creating the checklist. In most cases animals were photographed and identified using literature (Smith 1931(Smith , 1935(Smith , 1943Ahmed et al. 2009;Grimmett et al. 2011;Purkayastha 2012;Menon 2014).

RESULTS
During this study a total of 332 species of terrestrial vertebrates were recorded. Birds were found to be the most diverse group accounting for 214 species, followed by reptiles (57 species), mammals (36 species) and amphibians (25 species).
Amphibia: A total of 26 species of amphibians representing seven families were encountered. Among these, a single species is Vulnerable, four species are Data Deficient and 21 species are Least Concern (IUCN 2017). Of these, 11 species are included in Schedule IV of Indian Wildlife Protection Act, 1972 (IWPA) and rest were non-scheduled species (Table 1; Images 1-16).
Reptilia: A total of 53 species of reptiles representing eleven families were encountered from Guwahati City during the present study. Among these, a single species is Extinct in the Wild (Black Softshell Turtle), two species are Endangered, five are Vulnerable, 31 species are Not Evaluated and 14 species are Least Concern as per the

Conservation status
The conservation status of about 60% of the reptilian fauna recorded from Guwahati is yet to be evaluated (IUCN 2017), creating conservation concerns. Of all the turtles mentioned here, most of these are found in temple ponds of Urgratara and Kamakhya. Though protected by law, unorganized turtle trade for flesh and as pet still continues within the city. There also exists illegal trade for local bird species such parakeets which are sometimes sold under the veil of exotic bird trade. Threats The major threats to the terrestrial vertebrates of Guwahati perceived during the study are: 1. Habitat destruction and alteration: Many of the green patches are cleared away for constructional activities. Even the hills are used for settlement more than ever before with the city becoming the economic hub of the region. Again these hills are continuously exploited for resources. The city itself is fast losing its floral diversity and many of the trees planted through afforestation program lack suitability to provide nesting sites for birds. Moreover, concrete structures are replacing the age old Assam type houses which used to have nooks and corners providing living space to birds. Stone quarries and felling of trees in the hills is making the situation worse (All India Disaster Mitigation Institute 2014). The blasting of dynamite in stone quarries has made many species leave the area and surroundings. The blasting activities adjacent to Deepor Beel poses a challenge to its birdlife.

Degradation and filling up of wetlands:
Most of Guwahati is reclaimed from wetlands and the process is a continuous one. As a result of the loss of wetland, we are losing out on a wide range of biodiversity which in turn is disturbing the local ecological balance. Due to filling up of the wetland, the city is under artificial floods more than ever before (All India Disaster Mitigation Institute 2014). Deepor beel, the biggest wetland of the city, suffers from degradation of water quality, encroachment, and development of industries around it. The wetland famous for its birdlife is fast losing its glamor with fewer birds visiting the place.

Lack of interest: Urban biodiversity
conservation gets the least priority in the conservation arena in the region. In fact, the term urban biodiversity is alien to many policy makers. Thus very few efforts are taken in the region for research and conservation of urban biodiversity.

DISCUSSION
Cities form less than 3% of the terrestrial surface of the Earth, but they are responsible for 78% of carbon emissions, 60% of residential water use, and 76% of the wood used for various industrial purposes (Grimm et al. 2008). On the other hand, urban trees absorb pollutants to improve air quality and reduce the effects of greenhouse gases and, in some cases, they may do so three times more effectively than adjacent exurban forests (Akbari 2002). Since urban ecosystem is a human modified one, human induced habitat alteration makes the ecosystem susceptible to invasion of non-native species (Aggarwal & Butsch 2012). In this study, we also found an invasive reptile, Hemidactylus flaviviridis Rüppell, 1835, which was initially restricted to the commercial area but now has started spreading to residential areas and having a negative effect on native gecko populations (Das et al. 2011). The gecko made its way to the city through the interstate transportation system. Similarly, introduction of exotic trees is a threat not only to native trees but Journal of Threatened Taxa | www.threatenedtaxa.org | 26 September 2018 | 10(10): 12299-12316  Rodrigues et al. 2004), human aspect in the framework of biodiversity is not well studied. India's population is currently about 30% urban and is expected to become 50% urban by about 2044 (Cities & Biodiversity Outlook 2012). All these point to the fact that our country will have more urbanized space than ever before with more proportion of biodiversity occupying these urbanized spaces. Thus we are in need of better understanding of the multidimensional aspect of urban biodiversity taking in consideration, the human aspect for formulating long term research and conservation policies.

Recommendations
1. Afforestation effort is to be hastened, but the selection of plant species is an important aspect. Often fast growing trees, usually exotic, are selected for the purpose rather than suitable trees, such as fruiting trees and trees which the birds generally prefer for building nests.

2.
Artificial living space, more specifically for birds has to be created by installing nesting boxes and bird feeders. Not only shall it help birds but shall also help generate interest amongst masses regarding conservation of urban biodiversity.

3.
Children's urban biodiversity tour is another important aspect that would help create awareness and conserve the biodiversity of Guwahati. These tours can be a part of schools ecological club program; can also be conducted through district administration. We can only save things we love and can only love things that we have seen, thus these tours shall serve the purpose of conservation in long run.

4.
Deepor Beel is one of the most sensitive spots in terms of wetland birds, with 104 species of wetland birds recorded by us in the year 2016 including the endangered Greater Adjutant Stork which has a population of around 240 in the wetland. Unfortunately, this wetland is facing dual problems. The wetland is degrading mainly due to anthropogenic activity, and there is a tug of war between the community and an administration unable to find common ground. The current need to secure the future of the wetland is to adopt an approach that includes water quality improvement of the wetland via bioremediation (bacterial treatment) and a study of the socioeconomic structure of community living around the wetland to provide alternative sources of livelihood to the community who are primarily fishermen (this may include promotion of local handicraft, skill development programme for handicraft using water hyacinth, ecotourism, development of fisheries in government land, etc.). The selective incentive can be provided to the fishermen to encourage "no-fishing" in breeding seasons to help increase the productivity of the wetland.

5.
Turtles are one of the most vulnerable groups of vertebrates with about half of the species threatened with extinction (Turtle Conservation Coalition 2011). Thus, through captive breeding programme with the stock in the temple ponds, and subsequently through release of the hatched turtles to the wild, we can boost the wild population of these threatened animals. The temple ponds can thus serve the role of a breeding, conservation and education centers in terms of turtles.