Quantitative observation of Forest, Urban, Crop land and Barren land cover of Nepal using MODIS Land Cover

Quantitative observation of Forest, Urban, Crop land and Barren land cover of Nepal using MODIS Land Cover: Correlation test with FAOSTAT and National Land Cover Monitoring System of Nepal





Introduction

Information of land cover (LC) reveals the use of the land and suggests the ongoing changes within the land surface, most times due to the human led activities. Observation of land cover helps in the environmental monitoring and management which helps for the sustainable use of land in multiple and varied aspects of agriculture, urban planning, disaster management. In this regard, land cover has always been the most important area of research and education to understand the ongoing environmental as well as ecological aspects from which the land use trends can be meaningfully elucidated. 


This short study aims to study the forest, urban, crop land, and barren land cover for the country Nepal using MODIS Land Cover Type from the year 2001 to 2022. The study further correlates the calculated land cover information with FAOSTAT and National Land Cover Monitoring System of Nepal.




Data and Methods

MCD12Q1.061 (MODIS Land Cover Type Yearly Global 500m) was used to calculate the area of four different land covers (forest, urban, crop lands and barren) from 2001 to 2022. MCD12Q1.061, the yearly land cover available at 500m resolution, is obtained from supervised classifications of MODIS Terra and Aqua reflectance data. Land cover types, derived from the International Geosphere-Biosphere Programme (IGBP) have been used which are available as ‘LC_Type1’ along with the other land cover types. 17 different classes are in ‘LC_Type1’ as listed in the Earth Engine data catalogue which can be accessed from the following link.



Classes 1, 2, 3, 4 and 5, which include different classes for the forests, were used for the forest class, class 12 for the crop land, class 13 for the urban or built up land and class 17 were used for the calculation for the four major land cover. Google Earth Engine, a cloud based remote sensing analysis platform using (JavaScript API), was used to calculate the area of the selected land cover types.



Correlation Test

Above  calculated areas of land use classes were correlated with the extracted land cover trends from the other two sources:

FAOSTAT Land Cover (LC): FAOSTAT LC accessible from: https://www.fao.org/faostat/en/#data/LC/visualize contains the land cover classes of the international standard system for Environmental and Economic Accounting Central Framework (SEEA CF).  The FAOSTAT LC information has been compiled from publicly available Global Land Cover (GLC) maps. Items in the FAOSTAT LC (Artificial Surfaces, herbaceous crops, Tree-covered areas and Terrestrial barren land were selected and downloaded in hectares for the country Nepal from the year 2001 to 2022.



National Land Cover Monitoring System of Nepal (NLCMS): NLCMS ( accessible from: http://nepal.spatialapps.net/nlcms) , developed by the Forest Research and Training Centre (FRTC), Nepal with technical support from SERVIR-HKH and multiple cooperators using freely available remote sensing data using Google Earth Engine (GEE). Four major land covers in hectares were used to extract the land cover trends for four major classes (Forest, Crop land, Bare soil, Built-up).



Results

Crop land and barren land were found in decreasing trends; 22,282.32 km sq. of crop lands in 2001 to 20,666.36 km sq. in 2022, and 14,938 km sq. of barren land in 2001 to 13,966.01 km sq in 2022 with slight increase in the last two years (Figure 1b, 1c). Urban area had the increasing trends with 3.13.4 km sq. in 2001 to 346.85 km sq in 2022 (Figure 1d). With 33,269.69 km sq. of forest area in 2001, the forests too had increasing trends over the years reaching 39,751.31 km sq. in 2022 (Figure 1a). 


a.

b.

c.

d.
Figure 1: Trends of Land Covers from 2001 to 2022


Decreasing agricultural area of the country of Nepal can be due to the increasing service industries of Nepal. The other major reason is due to the abandonment of the agriculture profession of Nepal in changing the economic situation of the country. This imbalance of the agriculture activities within the country has led to unemployment as the major cause of the migration to the urban areas further increasing the urban areas (Bhattarai et al., 2023). In Nepal, urban sprawls have been observed around the established urban centres along the road networks which remains in the increasing trends.. The barren land might have decreased  due to the increasing forest land cover. Increasing forest land cover has been noted due to the successful community forests within Nepal (Chhetri et al., 2021; Van Den Hoek et al., 2021).


Correlation analysis of crop land from MODIS LC with crop land area from NLCMS (0.84) and FAOSTAT LC (0.92) showed highly positive correlation. This was also true with the urban land area which showed a positive correlation of 0.86 with FAOSTAT LC and 0.97 with NLCMS. The correlation coefficients were slightly lower, resulting in 0.70 with FAOSTAT LC and 0.74 with NLCMS. For the barren land, however, the relations of MODIS LC calculated area was negatively correlated with -0.32 with FAOSTAT and -0.68 with NLCMS. This could be the result of how the three land covers have considered the bare land in the generative process.


Table 1: Correlation of MODIS LC with FAOSTAT and NLCMS

a. Crop Land

MODIS LCFAOSTATNLCMS
MODIS LC1.00
FAOSTAT0.921.00
NLCMS0.840.911.00

b. Urban land / Built in Area
MODIS LCFAOSTATNLCMS
MODIS LC1.00
FAOSTAT0.861.00
NLCMS0.970.711.00

c. Barren land

MODIS LCFAOSTATNLCMS
MODIS LC1.00
FAOSTAT-0.321.00
NLCMS-0.680.281.00

d. Forests

MODIS LCFAOSTATNLCMS
MODIS LC1.00
FAOSTAT0.701.00
NLCMS0.740.901.00




Conclusion

In this article, land cover trends of four major land covers (forests, crop land, barren land and urban land) were observed from the MODIS Land Cover which was further correlated with the trends obtained from the Nepal Land Monitoring System and FAOSTAT land cover. All other land covers showed positive coefficient correlation while the barren land showed negative correlation. Quantitative observations have captured the ongoing decreasing and increasing trends in the land cover in the country Nepal which can further be valuable in ongoing discourse of sustainable land use in Nepal. 




References:

* Bhattarai, K., Adhikari, A. P., & Gautam, S. P. (2023a). State of urbanization in Nepal: The official definition and reality. Environmental Challenges, 13, 100776. https://doi.org/10.1016/j.envc.2023.100776

* Chhetri, R., Yokying, P., Smith, A., Van Den Hoek, J., Hurni, K., Saksena, S., & Fox, J. (2021a). Forest, agriculture, and migration: contemplating the future of forestry and agriculture in the middle-hills of Nepal. The Journal of Peasant Studies, 1–23. https://doi.org/10.1080/03066150.2021.1978983

* Van Den Hoek, J., Smith, A., Hurni, K., Saksena, S., & Fox, J. (2021a). Shedding New Light on Mountainous Forest Growth: A Cross-Scale Evaluation of the Effects of Topographic Illumination Correction on 25 Years of Forest Cover Change across Nepal. Remote Sensing, 13(11), 2131. https://doi.org/10.3390/rs13112131


Supplementary Materials:

Earth Engine Codes: https://disk.yandex.com/d/1__Ine2GDvNOVQ