The three-sub indicator i.e. Land cover, land productivity, and SOC stocks were analysed to study land degradation and ultimately report the SDG 15,3,1 indicator for the Indian state of Goa. “Trends.Earth, an open-source plugin of QGIS software, was used to perform the analysis over the period of 2001 to 2021, with the target year as 2021. The results for individual sub-indicators are discussed below.
5.1 Land Cover Shift
For the study period, the land cover shift shows degradation, stable, and improving trends for different components. The study depicts a positive shift in tree cover, with an improvement of 9%. An increase of 300% is noted in Artificial build-ups. Components like grasslands and cropland showed negative or declining trends. Table 4 presents the shift in land cover from 2001 to 2021.
Table 4
The land cover trend from the initial period to the final period
Land cover categories | Initial area (sq. km) | Final area (sq. km) | Change in area (sq. km) | Change in the area (per cent) |
TC | 1,644.20 | 1,789.11 | 144.91 | 9% |
GL | 185.64 | 136.75 | -48.88 | -26% |
CL | 1,365.00 | 1,135.99 | -229.01 | -17% |
WL | 33.26 | 37.04 | 3.79 | 11% |
AL | 42.12 | 168.42 | 126.30 | 300% |
BL | 0.00 | 0.00 | 0.00 | 0% |
WB | 150.89 | 153.79 | 2.90 | 2% |
Figure 3 below represents the land cover map for the period between 2001 and 2021, which shows the major increase of artificial cover from 42.12 sq. km to 168.42 sq. km.
The land cover transition is mostly along the coastal regions, which act as a major tourist attraction for the state of Goa. This transition is clearly depicted in Fig. 3.
Table 5
Land Cover by Type of Land Cover Transition in km2
| Land Cover categories at reporting period |
TC | GL | CL | WL | AL | OL | WB |
Land cover categories at the base year. | TC | 1,612.94 | 7.72 | 15.37 | 0.82 | 3.79 | 0.00 | 3.57 |
GL | 45.24 | 127.78 | 1.86 | 2.08 | 8.47 | 0.00 | 0.22 |
CL | 130.93 | 1.19 | 1,118.54 | 2.45 | 111.90 | 0.00 | 0.00 |
WL | 0.00 | 0.07 | 0.00 | 31.63 | 1.19 | 0.00 | 0.37 |
AL | 0.00 | 0.00 | 0.00 | 0.00 | 42.12 | 0.00 | 0.00 |
OL | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
WB | 0.00 | 0.00 | 0.22 | 0.07 | 0.97 | 0.00 | 149.63 |
Table 5 presents the land area by type of land cover transition for each component from the initial time of 2001 to the final reporting period of 2021. The artificial cover increase is the outcome of the growing tourism industry of Goa. The concentration of tourism growth in Goa is primarily focused on the regions of Bardez, Salcete, Tiswadi, and Marmagao. These areas account for approximately 66 per cent of Goa's Gross State Domestic Product (GSDP), making them the most economically developed regions in the state [16]. The infrastructure in these regions has played a crucial role in their development, enabling them to achieve high population densities and economic prosperity.
The small-scale industry sector in these regions is particularly significant, as it encompasses 70% of small-scale industries, attracts 78.5% of capital investment in such industries, and provides employment opportunities for 68% of the workforce [16]. These regions' strategic positioning and focus on tourism and industry have contributed significantly to Goa's overall economic growth and development. Additionally, supportive infrastructure has further facilitated establishing and expanding businesses in these key areas, driving economic progress and creating employment opportunities for the local population. Overall, the regions of Bardez, Salcete, Tiswadi, and Marmagao stand out as vital hubs of economic activity and growth within the state of Goa, playing a crucial role in shaping its economic landscape.
Overall, land covers a maximum area of 3,088.05 sq. km, with stable land cover accounting for 90.26% of the total land area. Also, 5.20% of land showed improved land cover with an area of 178.02 sq. km. This data is represented in Table 6
Table 6
| Area in km2 | % age of total land area |
Total land area under study | 3,421.1 | 100.00% |
Land area with improved land cover | 178.02 | 5.20% |
Land area with stable land cover | 3,088.05 | 90.26% |
Land area with degraded land cover | 155.03 | 4.53% |
5.2 Land productivity shift
The sub-indicator of land productivity has shown a significant improvement. The land cover transition is employed to study productivity individually as improving, stable, stressed, moderate decline, decline, and non-available data. SDG indicator areas are considered to be improved if they have "Improving" productivity, stable if they have "stable" or "stressed" productivity, and degraded if they are classified as in "moderate decline" or "declining." The tables below present this individual output.
Table 7
Improved productivity for land cover transition
| Land Cover categories at reporting period | |
TC | GL | CL | WL | AL | OL | WB | Total |
Land cover categories at the base year. | TC | 1,485.24 | 7.42 | 14.26 | 0.52 | 2.82 | 0.00 | 0.07 | 1,510.33 |
GL | 42.56 | 106.99 | 1.71 | 1.86 | 5.12 | 0.00 | 0.07 | 158.32 |
CL | 119.94 | 0.37 | 972.54 | 1.86 | 69.06 | 0.00 | 0.00 | 1,163.76 |
WL | 0.00 | 0.07 | 0.00 | 18.56 | 0.59 | 0.00 | 0.00 | 19.22 |
AL | 0.00 | 0.00 | 0.00 | 0.00 | 27.93 | 0.00 | 0.00 | 27.93 |
OL | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
WB | 0.00 | 0.00 | 0.22 | 0.00 | 0.30 | 0.00 | 32.74 | 33.26 |
| Total | 1,647.74 | 114.86 | 988.73 | 22.79 | 105.83 | 0.00 | 32.89 | 2,912.83 |
Table 8
Stable productivity for land cover transition
| Land Cover categories at reporting period | |
TC | GL | CL | WL | AL | OL | WB | Total |
Land cover categories at the base year. | TC | 109.21 | 0.22 | 0.74 | 0.22 | 0.67 | 0.00 | 0.00 | 111.07 |
GL | 2.45 | 15.51 | 0.15 | 0.15 | 2.45 | 0.00 | 0.00 | 20.71 |
CL | 8.24 | 0.67 | 100.80 | 0.45 | 27.02 | 0.00 | 0.00 | 137.18 |
WL | 0.00 | 0.00 | 0.00 | 5.79 | 0.45 | 0.00 | 0.00 | 6.24 |
AL | 0.00 | 0.00 | 0.00 | 0.00 | 8.54 | 0.00 | 0.00 | 8.54 |
OL | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
WB | 0.00 | 0.00 | 0.00 | 0.00 | 0.30 | 0.00 | 9.14 | 9.43 |
| Total | 119.91 | 16.41 | 101.69 | 6.61 | 39.43 | 0.00 | 9.14 | 293.18 |
Table 9
Stressed productivity for land cover transition
| Land Cover categories at reporting period | |
TC | GL | CL | WL | AL | OL | WB | Total |
Land cover categories at the base year. | TC | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
GL | 0.00 | 0.45 | 0.00 | 0.00 | 0.07 | 0.00 | 0.00 | 0.52 |
CL | 0.00 | 0.00 | 0.67 | 0.00 | 0.89 | 0.00 | 0.00 | 1.56 |
WL | 0.00 | 0.00 | 0.00 | 0.96 | 0.00 | 0.00 | 0.00 | 0.96 |
AL | 0.00 | 0.00 | 0.00 | 0.00 | 0.07 | 0.00 | 0.00 | 0.07 |
OL | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
WB | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 1.41 | 1.41 |
| Total | 0.00 | 0.45 | 0.67 | 0.96 | 1.04 | 0.00 | 1.41 | 4.53 |
Table 10
Moderate declining productivity for land cover transition
| Land Cover categories at reporting period | |
TC | GL | CL | WL | AL | OL | WB | Total |
Land cover categories at the base year. | TC | 10.62 | 0.07 | 0.37 | 0.07 | 0.30 | 0.00 | 0.00 | 11.43 |
GL | 0.22 | 2.97 | 0.00 | 0.07 | 0.37 | 0.00 | 0.00 | 3.63 |
CL | 1.78 | 0.00 | 22.04 | 0.00 | 8.46 | 0.00 | 0.00 | 32.29 |
WL | 0.00 | 0.00 | 0.00 | 1.11 | 0.00 | 0.00 | 0.07 | 1.19 |
AL | 0.00 | 0.00 | 0.00 | 0.00 | 3.05 | 0.00 | 0.00 | 3.05 |
OL | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
WB | 0.00 | 0.00 | 0.00 | 0.00 | 0.07 | 0.00 | 0.89 | 0.97 |
| Total | 12.62 | 3.04 | 22.41 | 1.26 | 12.25 | 0.00 | 0.97 | 52.55 |
Table 11
Declining productivity for land cover transition
| Land Cover categories at reporting period | |
TC | GL | CL | WL | AL | OL | WB | Total |
Land cover categories at the base year. | TC | 5.12 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 5.12 |
GL | 0.00 | 1.26 | 0.00 | 0.00 | 0.37 | 0.00 | 0.00 | 1.63 |
CL | 0.97 | 0.15 | 15.00 | 0.00 | 5.49 | 0.00 | 0.00 | 21.60 |
WL | 0.00 | 0.00 | 0.00 | 2.15 | 0.00 | 0.00 | 0.15 | 2.30 |
AL | 0.00 | 0.00 | 0.00 | 0.00 | 2.23 | 0.00 | 0.00 | 2.23 |
OL | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
WB | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.97 | 0.97 |
| Total | 6.09 | 1.41 | 15.00 | 2.15 | 8.09 | 0.00 | 1.11 | 33.85 |
Table 12
No data of productivity for land cover transition
| Land Cover categories at reporting period | |
TC | GL | CL | WL | AL | OL | WB | Total |
Land cover categlories at the base year. | TC | 2.75 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 3.49 | 6.24 |
GL | 0.00 | 0.59 | 0.00 | 0.00 | 0.07 | 0.00 | 0.15 | 0.82 |
CL | 0.00 | 0.00 | 7.50 | 0.15 | 0.96 | 0.00 | 0.00 | 8.61 |
WL | 0.00 | 0.00 | 0.00 | 3.05 | 0.15 | 0.00 | 0.15 | 3.34 |
AL | 0.00 | 0.00 | 0.00 | 0.00 | 0.30 | 0.00 | 0.00 | 0.30 |
OL | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
WB | 0.00 | 0.00 | 0.00 | 0.07 | 0.30 | 0.00 | 104.49 | 104.86 |
| Total | 2.75 | 0.59 | 7.50 | 3.27 | 1.78 | 0.00 | 108.28 | 124.17 |
Figure 3 represent change in productivity for the state of Goa with major area as improving with minor area as declining. The major trends of declining productivity are near Corlim region, consisting of land cover transition and an increase in artificial built-ups to support tourist accommodation and industrial estates. Further, the land area of Goa, with increased productivity, forms 85.14% of the total available land, which is nearly 2,912.83 sq km. This is represented in the table below.
Table 13
Overall productivity change
| Area in km2 | % age of total land area |
Total land area under assessment | 3,421.1 | 100.00% |
Land area with improved productivity | 2,912.83 | 85.14% |
Land area with stable productivity | 297.71 | 8.70% |
Land area with degraded productivity | 86.40 | 2.53% |
5.3 Soil Organic Carbon (SOC) Stocks Trend
SOC stocks are difficult to track due lack of data along with time and cost-consuming methods to study the change. SOC plays a fundamental role in the preservation of soil health, the functionality of ecosystems, and the guarantee of global food security. It is the primary measure to evaluate the above and below-ground carbon reserves. Compared to other indicators, alterations in SOC reserves linked to modifications in land utilisation and practices necessitate extended monitoring periods to assess the impact accurately. These variations, although significant, are relatively minor when juxtaposed with the vast quantities of carbon stored in the soil and the inherent fluctuations within these reserves. For individual class transition changes in SOC is tabulated.
Based on the difference, the change in SOC is plotted, representing a close association with changes in land cover trends and increased artificial built-ups. The overall SOC for the observed period shows stable behaviour, with more than 94.91%. However, there was a higher negative trend in comparison to improved SOC. The degraded SOC accounted for 4.27% against the improvement of 0.54%, and an overall negative change of -1.60% from the initial to the final year was observed.
Table 14
SOC trend from initial year to final year
| Initial soil organic carbon (tonnes/ha) | Final soil organic carbon (tonnes/ha) | Initial area (sq. km) | Final area (sq. km) | Initial soil organic carbon (tonnes) | Final soil organic carbon (tonnes) | Change in soil organic carbon (tonnes) | Change in soil organic carbon (percent) |
TC | 84.08 | 83.97 | 1,644 | 1,789 | 1,38,25,037 | 1,50,23,510 | 11,98,472.30 | 9% |
GL | 81.47 | 82.00 | 186 | 137 | 15,12,425 | 11,21,350 | -3,91,074.76 | -26% |
CL | 74.63 | 74.55 | 1,365 | 1,136 | 1,01,87,068 | 84,68,279 | -17,18,788.70 | -17% |
WL | 91.87 | 94.59 | 33 | 37 | 3,05,543 | 3,50,402 | 44,858.59 | 15% |
AL | 71.80 | 44.59 | 42 | 168 | 3,02,399 | 7,50,951 | 4,48,552.20 | 148% |
BL | 0.00 | 0.00 | 0 | 0 | 0 | 0 | 0.00 | 0% |
| | Total: | 3,270.22 | 3,267.32 | 2,61,32,472.05 | 2,57,14,491.67 | -4,17,980.38 | |
Table 15
SOC trend from initial to final year
| Area in km2 | % age of total land area |
Total land area: | 3,270.2 | 100.00% |
Land area with improved soil organic carbon: | 17.59 | 0.54% |
Land area with stable soil organic carbon: | 3,103.75 | 94.91% |
Land area with degraded soil organic carbon: | 139.59 | 4.27% |
Land area with no data for soil organic carbon: | 9.28 | 0.28% |
Percent change in soil organic carbon storage from initial year to final year: | − 1.60% |
Further, this change can be studied using the initial and final year map for SOC, which is represented below in Fig. 5.
5.4 SDG 15.3.1 Indicator
As suggested by the Good Practice Guidelines (GPG) of UNCCD, the 1OAO approach, as stated earlier, is used to obtain the SDG 15.3.1 indicator. Figure 5 shows the trends of the overall SDG 15.3.1 report from the initial to final years. This highlights the major degradation along the coastal regions associated with declining productivity and land cover change patterns.
A total of 2,776.66 sq. km of area was observed as improving, resulting in the heading of land degradation neutrality covering 81.16% of the total land. However, a degradation of 6.82% is observed for the area of 233.34 sq km, along with a stable area of 7% covering 239.42 sq km.
The change in land use pattern is plotted below. The bar chart represents the land cover trend over the initial to final year.
Table 16
| Area in km2 | % age of total land area |
Total land area under study | 3,421.1 | 100.00% |
Land area improved | 2,776.66 | 81.16% |
Land area stable | 239.42 | 7.00% |
Land area degraded | 233.34 | 6.82% |
Land area with no data | 171.68 | 5.02% |
5.5 Integrated Normalized Difference Vegetation (NDVI) Index
One widely used method to estimate NPP is by the mean of NDVI. The Normalized Difference Vegetation Index (NDVI) is a mathematical calculation that involves the comparison of near-infra-red (NIR) wavelengths, which are commonly reflected by healthy green plants, and red wavelengths that fall within the active spectrum and are generally absorbed by chlorophyll in healthy green plants. This index is a useful tool for remotely sensing vegetation health and monitoring changes in vegetation over time. The NDVI is suggested as the established vegetation index for evaluating SDG Indicator 15.3.1 when no evidence suggests that another index would provide greater accuracy in this context. It is widely recognized that the NDVI has proven to be a reliable and effective tool for assessing vegetation health and monitoring changes in land cover over time [17]. The integrated NDVI to time graph is plotted based on MODIS MOD13Q1 annually at a spatial resolution of 250m.
A linear regression model is depicted in the graph, with the coefficient of determination value r2 = 0.81, providing a visual representation of the upward trajectory observed in the integrated NDVI index spanning from the commencement year of 2001 to the culmination year of 2021, indicating a consistent growth trend over the analyzed period. Government policy approach toward sustainable tourism contributes toward improvement in SDG and integrated NDVI over the observed period.