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Remote sensing and geographic information system (GIS) in wildlife research

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March 11, 2017 by Species Ecology

Remote sensing and geographic information system (GIS) in wildlife research

Mohammed Ashraf

Remote sensing and geographic information system (GIS) based wildlife survey, monitoring, and evaluation procedures are relatively new areas for traditional biologists. Wildlife biologists at present have limited knowledge with respect to the scopes, power and the applicability of the GIS to better appraise their existing wildlife and habitat evaluation projects in tropical Asia. This situation is more precarious in tiger range countries particularly in Bangladesh despite the fact significant advances have been made in electronics and telecommunication technologies for the last decade. Apart from the ecological concern to help safeguarding the tigers and its habitats in Sundarbans-the mangrove ecosystem inhabiting remaining tiger population in Bangladesh, the grave threat that looms over the land of Bangladesh is climate change. The impact of climate change could be the biggest ecological insult for the tigers of the Sundarbans. Therefore, understanding and integrating the remote sensing and GIS tools are now becoming one of the modern conservation management priorities for government and the non-governmental organizations involved in wildlife and climate change research in South Asia. In Bangladesh context, establishing habitat evaluation procedure for the Sundarbans is becoming more urgent for assessing the suitable habitats for the tigers and for monitoring the impact of climate change over long term.

Remote sensing which provide spatial data is less used but strongly powerful tool to acquire up-to-date and accurate geo-spatial data essential for establishing habitat evaluation procedure. Wildlife managers have been using topographic maps to generate management and other maps of their interest for the past decades. Although technically complex, the remote sensing techniques have revolutionized the process of data gathering and map making. It can be applied to wildlife habitat inventory, evaluation, wildlife census and for generating mathematically accurate vegetation map both in spatial and temporal dimensions with extremely cost-effective and superb timeliness. For example, tiger ecology revolves around adequate numbers of prey that it hunts to survive and good sources of quality habitats (ecologically known as source pool) that provide cover, shelter and water for the tiger to breed and successfully raise the cubs. Tiger’s mortality rate is directly correlated with prey density and habitat integrity (unfragmented habitat). This basic ecological needs of tigers put everything into perspective in the context of designing tiger conservation landscape by integrating remote sensing and GIS utilities to evaluate the habitat qualities first, then identifying the source pools (as oppose to critical habitats) and finally mapping the source-sink dynamics/structure of the tigers in the Sundarbans and other high priority tiger conservation units across south Asia.

The technology that has given many more dimensions to the applicability of remote sensing based habitat evaluation or vegetation type map is geographic information systems or GIS in short. The discipline landscape ecology is benefited most with the availability of spatial analysis tool like GIS. Landscape ecology considers habitat as a mosaic of patches of vegetation with unique land form, species composition and disturbance gradient and focuses on parameters such as patch sizes, patch shapes, patch isolation, interspersion (adjacency of various land-uses/land-cover), juxtaposition (relative importance of adjacent patches), fragmentation, patchiness and so forth. All these parameters have direct bearing on the status of biodiversity within forest ecosystems. Spatial analytical capabilities of GIS allow quantifying all above parameters with the remote sensing based vegetation type map alone. Despite the fact habitat evaluation procedure (HEP) based on ecological science is well developed in North America, primarily by the US Fish & Wildlife Service, much of these standard evaluation procedures seem to escape the notice of conservation professionals focused on tiger conservation in South Asia. The need to incorporate these standard HEP particularly with the aim of protecting keystone species as such tigers in the case of Bangladesh, is well over due. The aim of any HEP is to evaluate an area on the basis of the sustainability of key habitat factors for certain species. That is, with detailed ecological information about a species, the characteristics of the habitat can be evaluated (using numerical rating schemes) on the basis of key habitat factors. The basic steps for the HEP are as follows:

The area being evaluated is divided into stands with relatively homogeneous cover types using remote sensing or ground based methods. (e.g. In the context of Sundarbans, different species of mangrove trees dominates different parts of the Sundarbans thus forming different mangrove stands, tall grasses also form unique stand, human disturbance periphery, buffer zones etc)

A species, Bengal tiger as an example, is selected and its sensitivity to habitat types (Mangrove stands, semi-aquatic grasslands, deltaic creeks and canals, buffer zones, human occupancy etc) and range requirement (prey density, forest cover, water supply, distance from human activities etc) is investigated.

A Habitat Suitability Index (HSI) is calculated for the tiger in the evaluation stands using tiger’s ecological parameters such as forest cover, prey density, distance proximity of the water supply from tiger’s territorial range etc. The HSI is defined as a value between 0 and 1 with the latter being the best quality of habitat in a defined area. The final aggregate value is an indication of the carrying capacity of the area for that particular species.

The general estimator for HSI then can be written in a simple linear equation:

HSI = ∑ {HSIi * ai}/A

Where, HSIi is the index for the ith stand, which has area ai and A is the sum of the stand areas (ai).

However the species selected (tiger is in our example) and the extent of information with respect to ecological and habitat parameters are of key importance in HEP. Once adequate data pertaining to the above-mentioned parameters is gathered and plugged into the estimator, HSI can then be calculated. With the power of GIS utilities, the HSI map can then be generated digitally with explicit spatial distribution patterns of the species of high conservation concern. One particularly strong element of GIS tool is its power to develop model predictions based on long-term ecological data sets of the species. The implication is remote sensing and GIS based tiger conservation survey in Bangladesh Sundarbans hold enormous prospects to not only mathematically pinpoint the best suitable breeding source pools but also to monitor the source-sink structure and dynamics in spatial-temporal scale. Over long-term data collections in a standardized HEP format, GIS database will have the capacity to model and predict source-sink and range contraction dynamics of tigers: extremely useful for making valid tiger conservation management decision against the prevailing anthropogenic threats and the impact of global warming in the Bangladesh Sundarbans.

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