Results and Discussion

Spatiotemporal land use dynamics:

The temporal land use analyses reveal the decline of vegetation cover during 1973 to 2017 with an unprecedented increase in built-up area (Table 3) in all these three regions (Fig. 3 and Fig. 4). PIE shows the decline of vegetation from 70.22 to 2.11 % (1973-2017), with an increase in built-up area from 0.33 to 87.39% (Fig. 3a). Now, PIE has more than 7500 registered industries and 75% of these industries are mainly engineering and garments sectors, which comes under the Peenya Industrial Association. The major growth is during 1992 to 2003 due to the expansion of major and small-scale industries under second phase (Fig. 4a). The major drivers of urban growth are major roads, major, small-scale industries, bus stops, bus depots, communication industries, banking, finance centers and residential areas etc. Similarly, WF region reflects the major changes in its vegetation cover from 2003 to 2008 (Fig. 3b). The vegetation cover has declined from 61.54 to 15.01 % with an increase in built-up area from 1.6 to 81.61 % by 2017 (Fig. 4b). The IT companies such as TCS, IBM, Dell, Accenture, Oracle etc., are located in this region. The large-scale residential apartments, biotechnology research centers and commercial complexes are also located in this region as part of the industrial expansion. The region has 85 % IT companies (4000 small to large scale industries), largest biotechnology companies (265). All these interventions have transformed the rural landscape into highly dense urban region covering 81.61 % with higher amounts of pollutions (air, water, etc.) (Ramachandra and Kumar 2010; Ramachandra and Bharath 2016; Ramachandra et al. 2017; Ramachandra et al. 2018b).

BSR has 86.35 % of the built-up area (Fig. 3c) at the cost of open spaces and vegetation cover from 55.17 to 2.66 % from 1973 to 2017 (Fig. 4c). The open spaces, parks cover was 37.67% earlier is now reduced to 7.23 % (2017). Mushrooming of multinational IT industries with large-scale residential apartments has resulted in the loss of vegetation cover. High-rise apartments, low-rise apartments and luxury apartments are blooming after 2003. The infrastructure developments with the widening of Hosur road, the elevated expressways etc. have led to the spread of commercial complexes towards east, southeast and south of Bangalore. The current urban growth across the regions are posing pressures on the biophysical environment while triggering waterbodies pollution, biodiversity loss, and drastic changes in the local climate. With an increase of impervious surfaces, (replacing soil and vegetation) has altered albedo and surface runoff water characteristics that significantly influence the processes of the surface atmospheric energy exchange at the local and regional scales (Madanian et al. 2018). These ecological and environmental changes have affected ecosystem services, ultimately influencing their ability to sustain the urban population and its infrastructure (Keshtkar and Voigt 2016).

Table 3 Land use analysis of three micro gradients

Fig. 4 Land use details during 1973 to 2017.

Spatial Pattern Analysis: The spatial pattern of LU changes during 1973 to 2017 is assessed through chosen landscape metrics (Fig. 5). CA shows PIE region has the least cover of built-up in 1973 and reached 805.59 hectares by 2017 and depicts the larger land use category. CA of WF shows vegetation cover dominated till 2003 and by 2012 built-up has become a most dominating feature, the same trend can be seen in BSR. NP metrics depicts PIE has a larger number of patches till 2003 indicating fragmentation. NP value has come down by 2017, with the formation of intermediate patches, and resulting in a single dense urban patch. The same trend can be observed in the other two regions with the decline of vital land uses due to the expansion of built-up area. LPI index shows that vegetation was a dominant class with the largest patch across all regions during 1973. But by 2003, the built-up region is the largest patch, due to an increase in built-up cover. PIE, WF region. LPI depicts dominance of built-up with an uneven distribution of other land use classes. AWMPFD shows built-up class values approach 2 (shapes with highly convoluted perimeter) due to intense urbanisation at the expense of open spaces. ROS depicts open space cover in the region, and least open space ratio exists across three regions. BSR shows ratio as 0.08 depicts dominance of a single class such as built-up cover from 1973-2017.

Table 4 Land use details of simulated (2017), projected (2022) and their accuracy.

Modelling and visualization of gradients: The visualisation and future land use transitions for three urban gradients are calculated using CA-Markov chain process considering land uses of 2003, 2008 and 2012. The transition probability matrices for three regions were estimated, which aided in the simulation and prediction of likely changes. This prediction has been done considering water bodies as a constraint with an assumption that water bodies would remain constant over all time period due to the stringent norms with awakened citizens. The model was validated by comparing the predicted versus the actual for the years 2012 and 2017 land uses with an allowable error of 0.15. Analysis and comparison of the simulated and actual land uses of 2012 and 2017 reveal that the CA-Markov model is a reliable estimator in terms of change quantification and for continuous space change modelling (Table 4 and Fig. 6). The PIE region shows a noticeable change in its land use due to existing facilities and the requirement of expansion of amenities to cater the demand of burgeoning population. Built-up is likely to cover 92.12% of PIE region at the cost of open areas and vegetation. 89% of the WF landscape will be urbanized by 2022 from 1.6 % (1973) at the cost of vegetation cover. This rural landscape has earlier catered the vegetable and milk demand of Bangalore. The urbanisation has replaced the regions under agriculture and horticulture crops with paved surfaces, posing serious challenges to the local ecology. BSR region is likely to be occupied up to 90% under built-up. The region has a good number of water bodies, but with the sustained inflow of untreated sewage and industrial effluents has adversely affected water quality (surface as well as ground water) and ecology. The irrational increase in built-up has impacted vegetation and open spaces in all these three micro gradients. The analysis of temporal changes in these growth centers highlights the need for policy interventions to regulate unrealistic urban expansions in the region.