Review Global conservation status of sponges James J. Bell, ∗ Emily McGrath, Andrew Biggerstaff, Tracey Bates, C´ esar A. C´ ardenas, † and Holly Bennett School of Biological Sciences, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand Abstract: Sponges are important for maintaining ecosystem function and integrity of marine and freshwater benthic communities worldwide. Despite this, there has been no assessment of their current global conservation status. We assessed their status, accounting for the distribution of research effort; patterns of temporal variation in sponge populations and assemblages; the number of sponges on threatened species lists; and the impact of environmental pressures. Sponge research effort has been variable; marine sponges in the northeastern Atlantic and Mediterranean and freshwater sponges in Europe and North America have received the most attention. Although sponge abundance has increased in some locations since 1990, these were typically on coral reefs, in response to declines in other benthic organisms, and restricted to a few species. Few data were available on temporal trends in freshwater sponge abundance. Despite over 8500 described sponge species, only 20 are on threatened species lists, and all are marine species from the northeastern Atlantic and Mediterranean. Of the 202 studies identified, the effects of temperature, suspended sediment, substratum loss, and microbial pathogens have been studied the most intensively for marine sponges, although responses appear to be variable. There were 20 studies examining environmental impacts on freshwater sponges, and most of these were on temperature and heavy metal contamination. We found that most sponges do not appear to be threatened globally. However, little information is available for most species and more data are needed on the impacts of anthropogenic-related pressures. This is a critical information gap in understanding sponge conservation status. Keywords: environmental impacts, freshwater, marine, sponge porifera Estado Global de la Conservaci´ on de Esponjas Resumen: Las esponjas son importantes para mantener la funci´ on del ecosistema y la integridad de las comunidades bent´ onicas en aguas dulces y marinas a nivel mundial. A pesar de esto, no ha habido una evaluaci´ on sobre su estado actual de conservaci´ on global. Evaluamos su estado, tomando en cuenta la distribuci´ on de esfuerzos de investigaci´ on, patrones de variaci´ on temporal en las poblaciones de especies y sus ensamblados, el n´ umero de esponjas en listas de especies amenazadas y el impacto de las presiones ambientales. El esfuerzo de investigaci´ on ha sido variable; las esponjas marinas en el noreste del Atl´ antico y el Mediterr´ aneo y las esponjas de agua dulce en Europa y Am´erica del Norte son las que han recibido la mayor atenci´ on. Mientras que la abundancia de esponjas ha incrementado en algunas localidades desde 1990, esto ha sucedido m´ as com´ unmente en arrecifes de coral, en respuesta a las declinaciones de otros organismos bent´ onicos y se ha restringido a algunas especies. Pocos datos sobre las tendencias temporales de la abundancia de esponjas de agua dulce estuvieron disponibles. A pesar de que hay m´ as de 8, 500 especies descritas de esponjas, s´ olo 20 se encuentran en listas de especies amenazadas y todas son especies marinas del noreste del Atl´ antico y el Mediterr´ aneo. De los 202 estudios identificados, los efectos de la temperatura, el sedimento suspendido, la p´erdida del sustrato y los pat´ ogenos microbianos han sido los m´ as estudiados intensivamente para las esponjas marinas, aunque parece que las respuestas son variables. Hubo 20 estudios que examinaron los impactos ambientales sobre las esponjas de agua dulce y la mayor´ ıa de estos fueron sobre la temperatura y la contaminaci´ on por metales pesados. Encontramos que la mayor´ ıa de las esponjas ∗ email james.bell@vuw.ac.nz †Current address: Departamento Cient´ ıfico, Instituto Ant´ artico Chileno (INACH) Plaza Mu˜ noz Gamero 1055, Punta Arenas 6200965, Chile Paper submitted May 3, 2014; revised manuscript accepted September 29, 2014. 42 Conservation Biology, Volume 29, No. 1, 42–53 C  2015 Society for Conservation Biology DOI: 10.1111/cobi.12447