Biodiversity

Abstract

The concept of biodiversity refers to (1) the number of types of natural ecological regions (ecoregions), (2) the number of native species within each ecoregion, and (3) the genetic variation within species (Janetos et al. 2008; Siikamaki 2008). For example, within the United States, vertebrate species richness naturally tends to be highest in southern areas and decreases with seasonally harsh winters in the north. Large states with boundaries that encompass a diverse array of ecosystems tend to contain a greater number of species than small homogeneous states. For this reason, Texas is second only to California in number of total species (Siikamaki 2008; Texas Environmental Profile 2008). Genetic aspects of biodiversity are illustrated by the global hotspot of endemism found in the isolated springs and cave systems of the Edwards Plateau, a natural legacy unique to Texas. Twelve major natural regions (ecoregions) are currently recognized within Texas (Fig. 5.1), ranging from deserts to prairies and pine forests, from mountains to coastal marshes (Griffith et al. 2007). Within each ecoregion, the landscape is further subdivided into vegetation types that correspond to variations in land and water features. This biologically diverse landscape represents a natural living library for scientists tracking the changes associated with climate change. Across the continent, the effects of climate change include not only redistribution of resident species but also the timing (phenology) of reproduction in resident species and arrival of migrant species (Janetos et al. 2008). This reshuffling of biotic communities is likely to result in ripples up and down the food chain, which are difficult to predict with the limited information currently available. Projecting impacts of climate change on biodiversity is a challenge for scientists and decision makers (Powledge 2008). Systematic scientific analysis of the problem is lacking for the state of Texas, so in this chapter we will review hypotheses derived from national and global studies (Janetos et al. 2008) while emphasizing the need for a more in-depth approach to adaptive management of biodiversity in Texas based on strategic monitoring and research. To be consistent with other chapters, this preliminary application of theory will be based on the range of scenarios of climate change projected for Texas (Chapter 1). Trends projected from historical data, however, have not always been consistent with projections of global climate models (Chapter 2). This discussion will show that many other factors, such as aquatic systems (Chapters 3 and 4) and growth of human populations (Chapters 6 and 7), probably will interact with climate in determining changes in the distribution of native flora and fauna across Texas. In particular, uncertainties associated with changes in human populations, land use, water use, seasonal rainfall, the rate of climate change, and climatic variability (e.g., storms, droughts, and freezes) make it very difficult to make statewide projections about changes in biodiversity. Therefore, this chapter first presents background information about known threats to biodiversity and uncertainties regarding projected changes. Second, we outline some general principles about the potential effects of climate change on biodiversity. Third, we describe the natural regions of Texas to illustrate both the richness of the natural heritage of the state and the reasons ecological changes would be expected to differ for each region. Predicting exactly how these changes are likely to occur would require a regional analysis beyond the scope of this chapter. Finally, at the conclusion of the chapter, we recommend the types of studies and strategies needed to manage biodiversity in Texas. The urgent need for decision makers to support an integrated and systematic research program will be made very evident. (Figure Presented). Copyright © 2011 by the University of Texas Press. All rights reserved.