Assessing desertification

VERÓN, S.R., PARUELO, J.M. AND OESTERHELD, M.

JOURNAL OF ARID ENVIRONMENTS

Año: 2006 p. 751 - 763

0140-1963

Abstract It is widely recognized that deserti .cation is a serious threat to arid and semiarid environments — which cover 40%of the global land surface and are populated by approximately 1 billion humans. Given the potential relevance of this problem,it is surprising that there is no consensus on the proper way to assess the deserti .cation status of a piece of land.During the last 70 years,con .icting de .nitions have produced both different assessment methodologies and divergent estimates. Contrary to conceptual issues on deserti .cation,assessment methodologies have not been reviewed comprehensively.Here,we critically review the most common methodologies to assess deserti .ca- tion,and describe their principal consequences on scienti .c and social arenas. We show that deserti .cation assessment has shifted from simple appraisals of the interannual movement of desert boundaries to complex multivariate .eld surveys,to practical methodologies based on indicators of ecosystem functioning,such as rain use ef .ciency.Although often regarded as an evidence of stagnation and failure,these methodologies re .ect the progress that deserti .cation ecology has experienced.Future challenges for properly assessing deserti .cation are (1)the lack of reference situations against which actual deserti .cation could be compared,and (2)the dif .culties that appear when deserti .cation operates through structural rather than functional ecosystem changes. The coexistence of con .icting de .nitions and divergent estimates negatively affects societal perception,leading to scepticism and,ultimately,to a delay of eventual solutions.Societies must recognize the progress deserti .cation ecology has made,leave behind concepts that no longer represent current knowledge,grasp the opportunity to better assess the extent and intensity of the problem,and,for the time being,realize that assessing deserti .cation is an unsolved issue. r 2006 Elsevier Ltd.All rights reserved.2006 Elsevier Ltd.All rights reserved. Keywords: Deserti .cation;Methodology;Precipitation marginal response;Quanti .cation;Rain use ef .ciencyDeserti .cation;Methodology;Precipitation marginal response;Quanti .cation;Rain use ef .ciency