Aproximacion a El Estado De Amenaza De Comunidades Ecológicas

Review

Assessing the Threat Status of Ecological Communities
EMILY NICHOLSON,∗ †∗∗ DAVID A. KEITH,‡ AND DAVID S. WILCOVE†§
∗

Imperial College London, Silwood Park Campus, Manor House, Buckhurst Road, Ascot, Berkshire SG5 7PY, United Kingdom, email e.nicholson@imperial.ac.uk †Woodrow Wilson School, Princeton University, Princeton, NJ 08544, U.S.A. ‡New South Wales Department of Environmentand Climate Change, Sydney, NSW, Australia §Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, U.S.A.

Abstract: Conservationists are increasingly interested in determining the threat status of ecological communities as a key part of their planning efforts. Such assessments are difficult because of conceptual challenges and a lack of generally acceptedcriteria. We reviewed 12 protocols for assessing the threat status of communities and identified conceptual and operational issues associated with developing a rigorous, transparent, and universal set of criteria for assessing communities, analogous to the International Union for Conservation of Nature (IUCN) Red List standards for species. We examined how each protocol defines a community and itsextinction and how each applies 3 overarching criteria: decline in geographic distribution, restricted geographic distribution, and changes to ecological function. The protocols vary widely in threshold values used to assess declines and distribution size and the time frames used to assess declines, leading to inconsistent assessments of threat status. Few of the protocols specify a scale formeasuring distribution size, although assessment outcomes are highly sensitive to scale. Protocols that apply different thresholds for species versus communities tend to require greater declines and more restricted distributions for communities than species to be listed in equivalent threat categories. Eleven of the protocols include a reduction in ecological function as a criterion, but almost allassess it qualitatively rather than quantitatively. We argue that criteria should be explicit and repeatable in their concepts, parameters, and scale, applicable to a broad range of communities, and address synergies between types of threats. Such criteria should focus on distribution size, declines in distribution, and changes to key ecological functions, with the latter based on workable proxiesfor assessing the severity, scope, and immediacy of degradation. Threat categories should be delimited by thresholds that are assessed at standard scales and are logically consistent with the viability of component species and important ecological functions.

Keywords: classification protocols, conservation status, IUCN, NatureServe, red list, threat categories, threatened species lists
Evaluaci´n del Estatus de Amenaza de Comunidades Ecol´ gicas o o

Resumen: Los conservacionistas cada vez est´ n m´ s interesados en determinar el estatus de amenaza de a a comunidades ecol´ gicas como parte de sus esfuerzos de planificaci´ n. Tales evaluaciones son dif´ciles debido o o ı a los retos conceptuales y la carencia de criterios aceptados por la generalidad. Revisamos 12 protocolos para laevaluaci´ n de estatus de amenaza de comunidades e identificamos aspectos conceptuales y operativos o asociados con el desarrollo de un conjunto de criterios rigurosos, transparentes y universales para evaluar comunidades, an´ logo a los est´ ndares para especies de la Lista Roja de IUCN. Examinamos la definici´ n a a o de una comunidad y su extinci´ n en cada protocolo y c´ mo aplica tres criteriosgenerales: declinaci´ n en o o o distribuci´ n geogr´ fica; distribuci´ n geogr´ fica restringida y cambios en la funci´ n ecol´ gica. Los protocolos o a o a o o var´an ampliamente en los valores umbral utilizados para evaluar declinaciones y distribuci´ n y en los ı o

∗∗ Address for correspondence: Imperial College London. Paper submitted February 14, 2008; revised manuscript accepted...