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Table 1 Spatial impact indicators calculated to evaluate anthropogenic impacts in Mexico

From: A spatial framework for detecting anthropogenic impacts on predator-prey interactions that sustain ecological integrity in Mexico

Indicator Formulation Definition and interpretation References
Land transformation Maximum value of a focal function of the amount of transformed landscape (e.g., cropland, rangeland, urban, agricultural irrigation) The amount of habitat loss and fragmentation within distribution areas of apex predators that is primarily driven by land use change Adapted from Riitters et al. (2002)
Inhospitable environment Variety value of a focal function of the different types of the transformed landscape (e.g., cropland, rangeland, urban, irrigated agriculture) The variety (e.g., the different land cover types) of the landscape transformation can be also expressed as the number of inhospitable environments that a top predator may encounter within its home range Adapted from Geneletti (2004)
Human activity A maximum value composited image was obtained by using a focal-mean function of the intensity of the human settlement index (HSI) within the home range of each apex predator. HSI is obtained from remotely sensed information of DSMP/OLS satellite observations of anthropogenic night-time brightness:
\( HSI=\frac{\left(1-{NDVI}_{\mathrm{max}}\right)+\left({OLS}_{nor}\right)}{\left(1-{OLS}_{nor}\right)+{NDVI}_{\mathrm{max}}+{OLS}_{nor}\ast {NDVI}_{\mathrm{max}}} \)
NDVImax =  MAX  (NDVI1, NDVI2…, NDVIn)
\( {OLS}_{nor}=\frac{OLS-{OLS}_{\mathrm{min}}}{OLS_{\mathrm{max}}-{OLS}_{\mathrm{min}}} \)
Where OLSnor is the normalized value of the DSMP/OLS DN image. OLSmin and OLSmax are the minimum and maximum values in the yearly DMSP/OLS image
Remotely sensed estimates of human activity using the DMSP/OLS satellite observations of anthropogenic night-time brightness. Night-time data provides quantitative data monitoring changes in demographics, economy, energy composition, and urban extent. Urban expansion has been achieved by using a combination of normalized difference of vegetation index (NDVI) from optical sensors (MODIS) and DMSP/OLS night-time lights. The HS indicate areas with human activity in a 0 to 1 range of values.
A composite pixel-by-pixel maximum value of the focal-mean maps represents collectively the maximum impact of human activity within the spatial home range of the apex predators
Adapted from Ma et al. (2012, 2015); Huang et al. (2016)
Human settlement avoidance The avoidance of human settlements was calculated as a function of the point density within the apex predators’ home range (the greater density of human localities within a home range, the greater avoidance) Here, avoidance is as a density function of point features in the landscape, which represents human settlements (points). Then, avoidance is an inverse function of the distance to the major source or barrier, i.e., the greater the distance to the barrier, the lesser avoidance (or higher mobility) Adapted from Geneletti (2003, 2004)
Highway and road avoidance Road and highway avoidance is as a density function of linear features in the landscape, which represents two types of features, i.e., linear infrastructure of highways and roads. Road and highway avoidance were obtained by calculating the Euclidean distance from a source (e.g., road or highway), and then filtered within the home range of every apex predator Infrastructure avoidance results in the impairment of animal movement patterns. The primary effect of roads is road mortality, elevated predation and human hunting. Road avoidance due to traffic noise is another differential source of ecological impacts, which differentiate the effects of highways and rural roads, and it is probably more important than road-kill Adapted from Geneletti (2003, 2006)
Forman and Alexander (1998)
Laurance et al. (2009)
Zarco-González et al. (2013)