to measure suspended sediments and chlorophyll concentrations spatiotemporally based on empirical relationships with radiance or reflectance (Ritchie and Cooper 1991; Ritchie et al. 1994).
Figure 2.4 Development of thematic maps and their integration for the prioritization of activities in a watershed using GIS. Based on Georgoussis et al. (2009).
2.2.4 Agriculture
The plants interact with the sunlight differently based on the observed wavelengths. The incident solar radiation can either be transmitted, absorbed, or reflected. The pattern of transmittance, reflectance and absorbed part of electromagnetic (EM) radiation provides essential insight to acquire information about plant physical and physiological status. Such as the absorbance bands of EM radiation (i.e. short wave infrared – SWIR 1 near 1.5 μ and short wave infrared‐ SWIR 2 near 2.5 μm) suggests the moisture availability in plants and vegetated landscapes. The health of forests or the photosynthesis activity by chlorophyll can be detected by analyzing the photosynthetic active radiation (PAR) range of EM waves where utilization of PAR is manifested as low reflectance of PAR in 0.6–0.7 μm range. Relating to their structural and biomass properties, leaves exhibit high reflectance and transmission in the near‐infrared spectral region (0.7–1.3 μm) (Tucker 1979; Avery and Berlin 1992). The structure of leaf area and plant canopy is also generally related to the reflectance patterns (Rautiainen and Stenberg 2005; Disney et al. 2006) which play a key role in growth monitoring. The absorption of radiation in the shortwave infrared region (1.3–2.5 μm), is mostly dominated by water and some biochemical components present in leaves. The phenological stages of plants and their interaction with different environmental aspects can be translated into unique signal patterns. These patterns or changes in electromagnetic radiation reflectance can then be interpreted and monitored using satellite data (Sharp et al. 1985; Blazquez and Edwards 1986; Curran et al. 1990; Miller et al. 1990; Pen Uelas et al. 1995; Kokaly 2001; Aparicio et al. 2002; Steddom et al. 2005; Disney et al. 2006; Guerif et al. 2007; Chen et al. 2010). The Chlorophyll content in vegetation is linked to the photosynthesis process and can be detected using the remotely sensed signature of selected EM wavelengths. Remote sensing signatures can further be linked to the various levels of stresses a plant may be facing. Thus remote sensing serves as a useful tool for monitoring the global health of vegetation (Gitelson and Merzlyak 1996) to suggest for water content and biomass of a vegetated landscape. This exemplifies the use of spectral signature in monitoring vegetation and its different parameters such as leaf area index, growing season, water stress, chlorophyll content, leaf structure, etc.
Figure 2.5 Applications of geospatial techniques for crop monitoring and management.
Precision agriculture is a site‐specific crop management prescriptions relying on information that can be measured using remote sensing for different crops across varying spatial and temporal scales. This system utilizes the power of modern technologies and information sources, including remote sensing, GIS, and GPS (Figure 2.5). Remote sensing supplements cost‐effective data for developing plans for precision agriculture. At the same time, the geographical information system provides a robust and flexible environment for the storage, processing, manipulation, analysis, and displaying of multiple spatial layers that can be used for the monitoring of agriculture and formulating a decision support system. Satellite imagery can be used for mapping discrete land cover and land use and for estimating other parameters of vegetation using spectral signatures (Steininger 1996).
Agriculture is the primary consumer of water, utilizing more than 70% of the global freshwater. Therefore, the role of irrigation water plays a significant in increasing the productivity of the land. Evapotranspiration (ET) from land surfaces is one of the key components of the water balance responsible for water loss. Evapotranspiration is of prime interest for various environmental applications, like optimization of irrigation water, irrigation system performance, water deficit for crops, etc. Also, poor irrigation timing and insufficient water application are common factors responsible for limiting agriculture production in many arid and semi‐arid agricultural areas. To address these issues, geospatial technology has emerged as a powerful tool to monitor irrigated lands over various climatic conditions and locations over the last few decades. It aids in determining when and how much to irrigate by monitoring the water status of plants. This is done by measuring evapotranspiration rates and by estimating crop coefficients. Efficient use and monitoring of surface water using geospatial techniques have recently attracted the interest of irrigation water policymakers.
2.2.5 Combating Desertification
Desertification is an extreme type of condition faced worldwide. Remotely sensed data and geospatial techniques provide important information for assessing desertification and its mapping at a local and global extent. It is a change in land condition that was not desertic into desert type landscapes and is closely linked to factors like population growth, improper farming practices, and widespread crops in naturally fragile environments. It occurs due to a lack of water reserves, humus‐depleted soils, scarce vegetation, and repeated plowing. The consequences of desertification can be dreadful for societies. Geospatial technology is utilized to determine the soil types, vegetation classification, land use classification, and nutrient availability in a region. Integration and weighted overlay of various factors in a GIS system result in vegetation, climate, soil, and management indices. The final product created after superimposing other indices creates a desertification sensitivity index. This index can help assess the stage of desertification of the study area (Lamqadem et al. 2018; Bedoui 2020).
2.2.6 Biodiversity Management
Biodiversity monitoring is essential for developing an adequate and timely management plan to safeguard the losses witnessed due to extreme human pressure or other natural causes. The LULC maps can be prepared using remote sensing observations and geospatial tools for understanding the rate of change of one land use category into another. Such assessment helps policymakers in developing plans that are effective in biodiversity conservation and management. This helps to ensure sustainable development and understanding of human activities' effect within and around protected areas. Geospatial data such as aerial and satellite photographs can be used to manage flora and fauna by determining the presence and distribution of vegetation and invasive species within a protected area (Kumar et al. 2019b). It helps in determining the extent of vegetation, water and food availability for animals in different seasons of the year. The animal census is usually assisted nowadays by aerial photographs or camera trap methods, which is again a useful application of geospatial technologies. Geospatial tools can also be used to show the intrusion of humans into protected areas and animal movements outside the protected areas. This is useful in resolving human‐wildlife conflicts. GPS technology can be utilized to monitor the activity of endangered species and protect them from poachers. GIS and remote sensing tools can also be used for conducting environmental impact assessment (EIA) of different projects, including building construction, road construction, pipe ways, dams, etc., within protected areas. Therefore, geospatial data has become essential in biodiversity management practices.
A study in Malaysia produced LULC for the Wildlife Reserves study area using the supervised classification of Landsat images and geospatial technologies. Different classification approaches
