Introduction
Landscape refers to a portion of heterogeneous terrain with the interacting ecosystems and is characterized by its dynamics, which are governed by human activities and natural processes (Ramachandra et al. 2012a). An Ecosystem is characterized by several unique biotic and abiotic components and its interactions among them. Interactions of these components amongst themselves and with each other happen through processes of nutrient cycling and energy flows. The anthropogenic land use and land cover (LULC) changes have been the major driver of the landscape changes at local levels. Unplanned developmental activities with the uncontrolled exploitation of natural resources and accelerating rates of LULC changes have led to the degradation of the ecosystem, evident from barren hilltops (Ramachandra and Bharath 2018), conversion of perennial streams to seasonal ones (Vinay et al. 2013), loss of livelihood, reduction in productivity, alteration in temperature (Ramachandra et al. 2018a), etc. LULC change analyses using temporal remote sensing data aid in understanding the spatio-temporal patterns of land uses, which is useful in the regional planning with prudent management of natural resources and good governance (Bhatta et al. 2010; Ramachandra et al. 2012a, b; 2018b).
Forests form an important component of a landscape and perform basic ecological and hydrologic functions, which help in sustaining water, conservation of biodiversity, regulating the air temperature, mitigate global warming (Ben-Zhi et al. 2005; Bharath et al. 2013; Naughton-Treves et al. 2005; Saxe et al. 2001), etc. Forests are the repository of natural resources, which support an array of biotic components, and cover only 30 percent of the land area of which only 20% are contiguous intact forests (WRI 1997; FAO 2010). Humans have been influencing the forested landscape through the clearing of native forests for various uses which in turn have degraded these ecosystems fragmenting it into patches. These biodiversity reserves are progressively being degraded or surrounded by urban environments or by agriculture and thus making them isolated fragments. Fragmentation is the breaking up of a landscape, habitat, ecosystems, or land use types into smaller parts (Forman, 2014), which results in the decreased size of the contiguous forests leading to the loss of connectivity between populations and the similar ecosystems (Griffiths et al. 2000; Fahrig 2003; Ramachandra et al. 2016a). Fragmentation and consequent deforestation is a major issue for mitigating climate changes and conservation of forests. Anthropogenic pressures on forest landscapes result in a complex pattern of forest structure with devoid of connectivity (Reddy et al. 2013). Connectivity among patches places a major role in species survival and conservation. Establishing the connectivity between the forest fragments can aid in conserving the overall ecosystem. The patch size quantification also assists to analyze the relationship between the number of species occurring and the patch size and also narrates the probable loss in species due to loss of forest cover (Jha et al. 2005). Patch size information aid in the fragmentation assessment and helps in assessing their role in maintaining biodiversity (Mandal et al., 2020). Increase in bisecting edges, perforated areas, with the decline of core areas are the consequences of anthropogenic induced fragmentation across the globe, which can be addressed systematically through comparing different time series data (Sharma et al. 2017). The extent of forest fragmentation has been quantified (i.e., the degree to which the forest is broken) through the assessment of changes in spatial characteristics and configuration of remaining patches (Saunders et al. 1987; Ramachandra and Kumar 2011).
The consequences of forest fragmentation are increased instances of human-animal conflicts, microclimatic changes, extirpation of species, increased isolation of remnant populations, alteration in the regional hydrological cycle by impacting the amount of evapotranspiration, infiltration and surface water runoff, uncontrolled emission of greenhouse gases (GHG) with the loss of natural sink, lowering of soil quality and inbreeding (Laurance et al. 1998; Boyle 2001; Ramachandra et al. 2018b). Hence, it is necessary to understand the extent of forest fragmentation, in order to develop appropriate mitigation measures for conservation and prioritization. The numerous techniques of forest fragmentation and forest connectivity using spatial data are available for quantitative estimation of landscape health and the ecological functions of individual patches. Spatial metrics have been applied extensively to describe the structures of a landscape with diverse land-use classes (Herold et al. 2002, 2003; Ramachandra et al. 2015), for explaining the interrelationship of intra and inter land uses (Ji et al. 2006; Huang et al. 2007; Ramachandra et al. 2012a) and to quantify temporal spatial heterogeneity (Lele et al. 2008). The average forest patches, size, forest patch density, number of forest patches, forest patchiness, forest continuity, edge density, shape measures and proportion of forest in the largest forest patch are the prime indices considered for assessment across the globe (Vogelmann 1995; Trani and Giles 1999). This information provides vital insights to the linkages between spatial patterns and ecological processes (Macleod and Congalton 1998; Madanian et al. 2018). Further, the analysis of forest fragments through the computation of ‘Pf’ and ‘Pff’ are easily comprehendible and are effective in categorizing the forest status (Ritters et al. 2000, 2004; Ramachandra et al. 2016a). The ecosystem also has a certain capability of withstanding external disturbances and thrives up to a certain limit, which is referred as the sensitivity or capacity of the respective ecosystem. Ecologically Sensitive Region (ESR) or ecologically fragile region, refers to a region that has low resilience and if disturbed by external influences either anthropogenic or natural, will find it difficult to be restored to its natural state (Gadgil et al. 2011). Landform, vegetation, geology, climate, social, cultural, and evolutionary history aspects are prime considerate in assessing the sensitivity of a region (McMahon et al. 2004). Ecosystems are not only characterized by their sensitivity but they are also significant in terms of the services that they provide (Wilkinson 2006) as well as their economic importance. An understanding of the various components of the ecosystem, their values and services, their interactions, and the anthropogenic effects (Ramachandra et al. 2016b) on them is crucial to sustainably manage through an ecosystem approach to conserve biodiversity and sustain natural resources (Ramachandra et al. 2017). However, most of the earlier endeavor lacks scientific rigor as well as eliciting information from the stakeholders.
The biodiversity hotspot regions such as the Western Ghats is considered ecologically or economically significant and/or sensitive, necessitates to delineate regions of importance to formulate appropriate conservation measures through the integration of technologies coupled with multi-criteria analysis. In this regard, the current work focusses on understanding LULC dynamics and temporal fragmentation of forests in Shimoga, located in the heart of Central Western Ghats. An attempt is made to understand the agents of forest fragmentation through a compilation of forest encroachments. The research also aims to identify and prioritize Ecologically Sensitive Regions (ESR) of Shimoga at village level based on the collection and compilation of primary data of ecological, geo-climatic and social aspects to assist in decision making towards the prudent management of natural resources.