Geodiversity and biodiversity in the Himalaya region: Quantifying spatial patterns and exploring linkages

Abstract

Geodiversity is the term that describes the variability of Earth's surface materials, forms, and physical processes. Conservation of geodiversity has become increasingly significant in recent decades since it has become apparent that geodiversity provides the abiotic preconditions for habitat development and maintenance and has a considerable influence on biodiversity. The Himalaya is one of the mountain systems showing the highest levels of geodiversity and biodiversity. The hypothesis for this research to be tested is that 'geodiversity can be a useful surrogate for biodiversity information in the Himalaya mountain system.' Jammu and Kashmir (J&K) and Sikkim, located in the subtropical western Himalaya and humid eastern Himalaya respectively, have been selected as two study areas within this global hotspot of biodiversity. To prove the hypothesis, the first approach of this research was to explore the geodiversity of Sikkim, J&K, and the Himalaya mountain systems, using topographical, pedological and climatological information, and to analyse the importance of geodiversity in the context of climate change and future conservation of natural resources. Quantification of geodiversity was followed by different methodologies in System for Automated Geoscientific Analyses (SAGA) open-source software. I used fuzzy logic to produce geodiversity information and a species richness map. A detailed database on species (flora) richness has been drawn from several studies. The total number of species in Sikkim is 5,087(in 7,096 km2), and in J&K, it is 5,656 (in 1,38,992 km2). The number of families is 245 in Sikkim and 266 in J&K, and the number of genera is 1,489 in Sikkim and 1,537 in J&K. The most dominant families in Sikkim are Asteraceae, Cyperaceae, Leguminosae, Rubiaceae, Rosaceae, Scrophulariaceae, Primulaceae, Gentianaceae, Euphorbiaceae, Ranunculaceae, and Lauraceae and the most dominant families in J&K are Asteraceae, Poaceae, Fabaceae, Cruciferae, Rosaceae, Labiatae, Cyperaceae, Ranunculaceae, Boraginaceae, and Caryophyllaceae. The highest number of species (around 1,864 to 2,146 species) in Sikkim is at an elevation between 1,000 to 2,500 m above sea level (asl). The highest species richness (around 1,000 to 1,800 species) in J&K is at an altitude between 1,500 to 4,000 m asl. The subtropical forest and tropical broadleaved forest vegetation zones have the richest species diversity (more than 1,600 species) in Sikkim. The number of species in J&K is less than 200 in the subtropical forest. Multiple regression analysis between species richness and other abiotic predictors showed very little difference in results for Sikkim and J&K. The generalised linear model (GLM) found that 68% and 67.6% of species richness can be predicted from the abiotic variables for Sikkim and J&K, respectively. The generalised additive model (GAM) with smoother function shows better results than does GLM, and the deviance explained in the model is 69.8% in Sikkim and 66.9% in J&K. The model also found that temperature and slope (inclination) are the significant predictors in Sikkim, and precipitation and slope (inclination) are the most noteworthy variables in J&K. Model accuracy was evaluated using threshold-independent (Area Under the Curve) measures. The GLM and GAM models in the study areas showed a lesser model prediction error than the geodiversity vs. species richness model, and GAM was the most suitable model for prediction. The quantified geodiversity index (GI) was 0.01–0.32 in Sikkim and 0–0.16 in J&K. The GI in the Himalaya range is 0.01–0.18, in which Sikkim has a relatively higher GI (0.05–0.18) than does J&K (0.01–0.12). This difference of geodiversity proves that hotspots in the eastern Himalaya have greater geodiversity than those in the western Himalaya. Lower elevation areas in Sikkim show low to moderate geodiversity, and temperate broadleaved forest and subalpine forest areas have high to very high GI (0.17–0.32). Vegetation cover in Kashmir Valley which has low geodiversity has low species richness. High to very high GI (0.08–0.16) and species richness exist in sub-alpine, and temperate zones in J&K. Moderate geodiversity in some parts of the Jammu division correlates with very high and medium species richness. Potential species richness compares the actual differences of the number of species per km2 in both study areas, which shows higher richness in Sikkim than in J&K. Quantified geodiversity and species richness showed a positive relationship accurately, which proves geodiversity information can surrogate biodiversity information for the Himalaya. The present method to measure geodiversity using widely available data has the potential to be used as a conservation planning tool even in remote areas such as the Himalaya.