Climate Change Effects, Adaptation, and Mitigation Techniques in Tropical Dry Forests

Introduction

Tropical dry forests cover almost half (i.e. 42%) of total tropical and sub-tropical forests of the world (Brown & Lugo, 1982; Murphy & Lugo, 1986). Tropical dry forests are defined on the basis of climatic limits (Gerhardt & Hytteborn, 1992; Portillo-Quintero, 2010). Forests that occurred in tropical regions with a climatic limits of pronounced drought period of 3-9 months, an average annual temperature of more than 17^oC, precipitation ranges from 200 to 2000 mm per year, and annual ratio of potential evapotranspiration (PET) to precipitation (P) exceeds one are termed as tropical dry forests (Murphy & Lugo, 1986; Mooney, Bullock, & Medina, 1995; Blasco, Whitmore, & Gers, 2000; Sánchez Azofeifa et al., 2005; Pennington, Lewis, & Ratter, 2006). Though the characteristics of the forests are difficult to be defined precisely, seasonally dry tropical forests are tree-dominated ecosystems unlike savannas. Trees of tropical dry forests are deciduous in nature, and generally grow on fertile soils (Ratter et al., 1973; Furley, 1992; Vargas, Allen, & Allen, 2008). Customarily having a closed canopy with woody flora these forests are dominated by the Leguminosae and Bignoniaceae (Pennington, Prado, & Pendry, 2000). Generally, tropical dry forests are found in the region where most of the months are dry and wet period is short. A long period without any precipitation characterizes the species of the forests, forcing them to adapt with and survive in the warm dry condition.

Tropical dry forests are the most threatened ecosystems in the world (Janzen, 1988; Hoekstra et al., 2005; Miles et al., 2006). These forests are the habitat of a large number of flora and fauna, but with the shrinkage of these forests to 10% from its original range (Janzen, 1988; Bruegmann, 1996; Juvik & Juvik, 1998; Allen, 2000; Cabin et al., 2000), it is now a highly vulnerable ecosystem. Though, the soil of this biome is much more fertile (Pennington, Prado, & Pendry, 2000) and these forests might help to mitigate climate change by storing carbon (Skutsch & Ba, 2010; Daniel et al., 2014), it remained overlooked by conservationists and researchers. More than 1600 inventories in the tropical dry forests revealed that these forests are the habitat of remarkably 6958 woody plant species (Kinver, 2016). Many of these species are endemic and among all woody species, about 40% are not grown elsewhere in the world, except in tropical dry forests (Kinver, 2016). Most interestingly, it has been found through molecular research that some species that grow in these forests are ancient (about >10 million years old) (Kinver, 2016). These forests are actually a museum of diversified species, particularly of the endemics (Trejo & Dirzo, 2000; Sánchez-Azofeifa et al., 2005). If any one species becomes extinct, it will be a great loss to the world. Moreover, tropical dry forests are affected by climate change since a long time (Parmesan, 2006; Phillips et al., 2010; Liu et al., 2013). Global climate change badly impacts on the species distribution (Peterson & Kluza, 2005). Owing to its biological and genetic importance, and its great potential contribution in the mitigation of climate change, tropical dry forests necessitate more concentration of the scientists and policymakers (FAO, 2001).