Mangroves of arid environments of Latin America

Abstract

On the west coast of South America oceanic and atmospheric conditions give rise to an extraordinarily dry landscape that restricts mangroves to deltaic environments, such as those of the Gulf of Guayaquil (Ecuador) and the Tumbes River (Peru), reaching their limit at just 05° 30′ S at the mouth of the Piura River (Peru). Mangrove development beyond this location is limited by unsuitable topography, aridity, prolonged droughts and extraordinary fluctuations in river flow. High soil salinities limit mangroves to very narrow fringes vulnerable to wipe-out during catastrophic flooding, as it occurs during ‘El Nino’ events. At Tumbes (03° 30′S) red mangroves reach 25 m in height and interstitial salinities are moderate (<40‰), due to fluvial inputs and a mesotidal regime. On the Atlantic side of South America water deficits limit mangrove development from Ponta Mangues Secos (02° 15′S) to south of the State of Bahia (18> S). Annual rainfall is >1000mm/y but there is a pronounced dry season and frequent droughts. Forest structure and biomass at maturity reflects the availability of subsidiary energies such as tides, streamflows and nutrients. Where these are present mangroves may develop uncharacteristically high structure but become very susceptible to slight changes in hydrologic regime. Marked structural gradients,’ massive tree mortalities and fluctuations in coverage are natural features of these landscapes.