It is getting hotter in here: determining and projecting the impacts of global environmental change on drylands

Abstract

Drylands occupy large portions of the Earth, and are a key terrestrial biome from the socio-ecological point of view. In spite of their extent and importance, the impacts of global environmental change on them remain poorly understood. In this introduction, we review some of the main expected impacts of global change in drylands, quantify research efforts on the topic, and highlight how the articles included in this theme issue contribute to fill current gaps in our knowledge. Our literature analyses identify key under-studied areas that need more research (e.g. countries such as Mauritania, Mali, Burkina Faso, Chad and Somalia, and deserts such as the Thar, Kavir and Taklamakan), and indicate that most global change research carried out to date in drylands has been done on a unidisciplinary basis. The contributions included here use a wide array of organisms (from micro-organisms to humans), spatial scales (from local to global) and topics (from plant demography to poverty alleviation) to examine key issues to the socio-ecological impacts of global change in drylands. These papers highlight the complexities and difficulties associated with the prediction of such impacts. They also identify the increased use of long-term experiments and multidisciplinary approaches as priority areas for future dryland research. Major advances in our ability to predict and understand global change impacts on drylands can be achieved by explicitly considering how the responses of individuals, populations and communities will in turn affect ecosystem services. Future research should explore linkages between these responses and their effects on water and climate, as well as the provisioning of services for human development and well-being.

Figure 1.

Examples of dryland vegetation. (a) Mixed shrubland dominated by Ericameria nauseosum in Utah, USA (photo by M. A. Bowker); (b) shrubland dominated by Chamaecrista cytisoides in Brazil (photo by R. Romao); (c) shrubland dominated by Quercus coccifera and Rosmarinus officinalis in Spain (photo by J. L. Quero); (d) Stipa tenacissima grassland in Morocco (photo by F. T. Maestre); (e) Festuca orthophylla grassland in Peru (photo by J. Monerris); (f) open woodland dominated by Eucalyptus populnea and Acacia aneura in Australia (photo by S. Soliveres); (g) shrubland dominated by Eulychnia acida in Chile (photo by C. Barraza); (h) grassland dominated by various Stipa and Festuca species in Argentina (photo by J. Gaitán); (i) Larrea cuneifolia shrubland in Argentina (photo by E. Pucheta); (j) savannah of Acacia totalis in Kenya (photo by V. Polo).

Figure 2.

Research efforts on global change conducted in drylands (indicated by dashed borders), according to the country where the work was carried out. To obtain data for this map, we searched for peer-reviewed field studies on this topic in the ISI web of knowledge database (http://www.isiwebofknowledge.com) published between 1899 and 2011 (see electronic supplementary material, appendix S2 for details). Dashed areas represent drylands, as defined by UNEP [3]. The studies from countries such as the UK mostly reflect research based on paleo-scales, when these regions were drylands.

Figure 3.

(a) Historically, there has been a lack of integration among biogeochemistry (BGC), sociology (SOC) and ecology (ECO) in global change research carried out in drylands, as shown in the Venn diagram for the number of publications on this topic. To obtain this diagram, we classified the dryland publication list obtained from our literature search (see the electronic supplementary material, appendix S2) into three disciplines—biogeochemistry, ecology and sociology—by adding those keywords and their possible seven combinations to this search. Areas are proportional to the number of publications, and the overlap between them indicates integrative efforts. (b) The present theme issue undertakes an integrative approach of biogeochemistry, ecology and sociology to offer a better understanding of how global environmental change will affect dryland ecosystems and their biota, including humans. Roman number position represents areas of expertise included in each manuscript of the theme issue: (I) Maestre et al. (this study), (II) Thomas [72], (III) Escolar et al. [65], (IV) Salguero-Gómez et al. [143], (V) González-Megías & Menéndez [68], (VI) Ban & Lai [156], (VII) Sala et al. [142], (VIII) D'Odorico et al. [149], (IX) Huber-Sannwald et al. [133] and (X) Dougill et al. [163].