Satellite Imagery of Sloth Bear Range in India and Bangladesh

Data Collection

Data and images were obtained from the Maryland Land Cover Facility using Landsat 7 satellite's Enhanced Thematic Mapper Plus (ETM+) sensor. The images are 30 x 30 meter resolution with a swath width of 185 kilometers. Bands 1-8 were downloaded for the purposes of this analysis and layered in particular fashions in order to provide a broad scope of analysis of the images. In this comparative study of Indian and Bangladeshi environmental conditions, images of the two countries will be analyzed in order to determine the most suitable habitat for the sloth bear. Additionally, policies such as the setting aside of land for nature reserves collected from ProtectedPlanet.net will be used to determine future conservation efforts of the bear species on the Indian subcontinent.
 

Images for the sloth bear range in India were acquired from the Orissa region of India on the Eastern edge of the subcontinent. The yellow border outlines the limits of the region of India and the transparent red square is where the images were obtained by Landsat 7 in November of 2011. 

Images for the sloth bear range in Bangladesh were taken by Landsat 7 in the northwestern region of the country near the border. The images were acquired in November 2000. 

Data Processing
The Visible

These images were created by layering the visible bands 1,2,3 (Red-3, Green-2, Blue-1) to create a visual depiction of what the areas look like from space to the naked eye. 

The first image is of India over the Orissa region of the country. The terrain is variable with patches of dense forest interspersed with rocky areas. This coastal habitat is home to a population of sloth bears who thrive in the forested areas. The bears tend to avoid coastal areas so their numbers nearer to the coast. Additionally, coastal areas tend to be more heavily developed and populated. The visible bands do not provide many levels of analysis other than what can be seen by the naked eye. It does, however, provide a useful reference for other levels of analysis such as the use of infrared bands and an NDVI index. These avenues will be explored in more detail.

The image taken of Bangladesh differs greatly from the previous image of India. One of the main differences in the visible signs of deforestation that are apparent in this image. The region appears to be sparsely vegetated with a very small amount of heavily forested areas making it an unsuitable habitat for a sizable sloth bear population. As is true with most of the members of the bear family, sloth bears are solitary animals who require a relatively large range that typically does not overlap very much with the range of others of its kind. Although signs of human settlement or development are not apparent, it is obvious that humans have had an effect on the landscape of this study site. These effects become even more apparent with further processing and analysis using different bands and indices of forest health.

The Infrared

The second images layers the red, near-infrared, and mid-infrared bands (3,4,5) in a specific fashion (Red-4, Green-5, Blue-3) produces the following images.

By using infrared bands, the vegetative composition of the region can be better understood. The dark orange areas correspond with the densely forested areas seen in the visible light image and therefore represent areas of high vegetation cover. Bodies of water are appropriately colored blue. The less densely areas are the grey-green color. The bears would most likely be found in the areas appearing as bright orange as they prefer to inhabit areas with high forest cover providing them with the resources and protection required for their survival. As can be seen in this image, the large expanses of forested areas in the Orissa region of India provides plenty of habitat possibilities for the solitary sloth bear making it a suitable environment for a sizable population of the species. 

Conversely, this highly deforested region of Bangladesh is not the optimal environment for the sloth bear as its forests have been removed and have not yet been able to grow back. This can be seen in the large extent of this area that appears in the grey-green color. The amount of orange colors denoting regions of dense vegetation is far less than the previous image and also very fragmented. Disconnected forest does not help in sustaining large populations of species as they are not allowed the space or range to properly distribute themselves. These images taken in relatively close proximity to each other differ greatly from each other as a result of policies protecting certain regions in India and the lack of these same policies in Bangladesh.

Normalized Difference Vegetation Index (NDVI)

The third images show the Normalized Difference Vegetation Index (NDVI) for the study region in Orissa, India and northwestern Bangladesh. This index is used in remote sensing to determine the amount of live vegetation in an area. Colors were assigned using color theory to ensure that the pattern of vegetated and non-vegetated land can be clearly understood with dark green depicted areas with an abundance of live vegetation and sienna colors areas with low levels of live vegetation. Essentially, NDVI gives the level of "greenness" of an area by combining the infrared and red bands to produce the amount of photosynthetic activity in an area. It is calculated by subtracting the visible light from the near-infrared and then dividing this number by the number produced from the near-infrared added to the visible. This results in a value between 1 and -1 with the former representing areas with high levels of photosynthetic activity and the latter areas with low levels. These numbers are assigned colors in ENVI to depict the level of greenness that particular region. 

India shows signs of live vegetation in the same areas with dense forests in the image containing the visible bands as well as the infrared image telling the same story. As you approach the coast, the amount of live vegetation declines steadily before reaching the ocean seen in blue. Also, a unique marine area is seen near the coast of Orissa providing a habitat to many different types of species. Typically, however, the sloth bear would not be found near these areas because of the brackish water and the lack of resources the species requires to survive in the wild. Also, the marshy land is not a suitable environment for the bear's main food source ants and termites. This fact alone disqualifies this marine area as a suitable environment for the sloth bear.

Bangladesh proves to be a much less suitable habitat for the forest-loving bears appearing to have far less area of live vegetation. The amount of photosynthetic activity is drastically less in this area as seen in the lack of large regions of the dark green color; the areas with dark green are extremely fragmented. Additionally, the sienna color is seen in patches throughout the study area representing areas with extremely low levels of live vegetation and subsequently, areas that are unsuitable habitats for the sloth bear. The lack of photosynthetic activity is resultant of deforestation in the area - as all the trees in the region are removed, the photosynthetic activity will inevitably decline. 

Protected Areas

This image uses bands 1-3 (visible) to depict the Orissa region of India overlaid with protected areas in this part of the subcontinent. The red outlines areas set aside by the Indian government as nature reserves strictly dedicated to the preservation of species in this area. One of the reserves is located on the coast surrounding the delicate marshlands which provide habitats for a large number of the world's species and are important breeding grounds for several endangered bird species. Noticeably, three of the reserves are circular in shape. This shape has been determined to be the optimal design strategy for nature reserves based on the concept of island biogeography. In this line of reasoning, decreasing the amount of edge and increasing the amount of interior area. As a result of this line of thinking, many of the nature reserves around the world are round in shape. The data for these protected areas was obtained from ProtectedPlanet.net, downloaded as shapefiles, and then overlaid onto the image of India in the visible bands. Sloth bears would thrive in the two circular reserves located in the densely forested protected areas located in the northwestern part of Orissa.

This section of Bangladesh appears to have only 2 protected areas in the study area. Additionally, the larger of the two appears to be deforested making it unsuitable for many of the species that have adapted to heavily forested areas in this region. It should also be noted that the design of these habitats does not optimize the amount of interior space as the reserves in India did. The irregular borders of the protected areas do not follow the guidelines for creating successful reserves. The sloth bear would have trouble finding the resources it requires in this protected part of the country and would therefore have a hard time surviving despite the measures taken to protect species in this region. This image was processed in the same way as the Indian image with shapefiles downloaded from ProtectedPlanet.

Conclusion

Sloth bear distribution on the Indian subcontinent has varied over time as human development encroaches on the species territory and deforestation threatens the health of the remaining forest. Analyses of these two different regions reveal the reasons why sloth bears remain in the areas that they are found today. India has the largest population of the species simply because it has the largest amount of land to allow the solitary species to distribute themselves as well as having the protection needed to maintain its numbers enforced by the government of the nation. Conversely, Bangladesh's lack of policy and rapid human development has left much of the suitable habitat for the sloth bear deforested or occupied by the human population. 

Satellite imagery was used to analyze the amount of deforestation as well as the state of the remaining forest cover in two study sites - one in India and the other in Bangladesh. These two areas presented very different landscapes despite their close proximity to each other. India has taken great measures to ensure the biodiversity of the nation is preserved. As a result, sloth bear habitat continues to thrive and allow the bears to continue their presence in this part of the world. Bangladesh was, historically, a region where sloth bears could be found. However, as a result of rapid deforestation and lack of protected areas, sloth bears are no longer found in the country. The differences in the two countries can be seen from the images acquired by the Landsat 7 satellite. The levels of analysis including infrared, normalized difference vegetation index, and overlay of protected areas in the regions paints a picture of what the state of these areas is. 

Future policies for the protection of the endangered sloth bear should include the preservation of vital habitat of the species including densely forested areas on the Indian subcontinent. With these measures in place, hopefully the species will act as an umbrella species protecting other organisms in the same area. Forests provide habitat for hundreds of thousands of the planet's species so, in protecting these vital habitats, many thousands of species can be preserved. Sloth bears inhabitat tropical and sub-tropical latitudes in some of the lushest habitats in the world. It is critical that these forests are maintained for the future of the species that require them for survival. The most effective way of going about the protection of these areas is through policy - that being said, more policies protecting the environment need to be instituted to protect these precious floral and faunal species.