Mangroves on the Edge: Anthrome-Dependent Fragmentation Influences Ecological Condition (Turbo, Colombia, Southern Caribbean)

Juan Blanco-Libreros,Edgar Estrada-Urrea

doi:10.3390/d7030206

Abstract

Marine protected areas are commonly seen as the most effective strategy for protecting mangroves from external human pressures but little is known about the role of public land-tenure contexts (dense settlements, agricultural or range lands and wild anthromes) on clearing rates, patch properties, and ecological condition. We addressed the following questions using a peri-urban to wild gradient along the anthropogenic coastal-scape in Turbo Municipality (Colombia, Southern Caribbean): Do the different deforestation rates observed under peri-urban, rural, military-protected and wild land-use-and-tenure contexts, promote distinctive fragmentation patterns? Do these patterns influence loggers’ access and ultimately ecosystem ecological condition? Loss rate (1938–2009) was the greatest peri-urban mangroves and positively correlated with urban edge and patch density. Pasture edge was highest in rural mangroves while mean patch area was higher in protected and wild mangroves. An Anthropogenic Disturbance Index (ADI) was strongly correlated with reduced mean patch area and increased patch density, due to increased trampling and logging, that ultimately promoted high densities of thin (diameter: <5 cm) Laguncularia racemosa trees but had no significant effect on the presence of a dominant benthic gastropod. In conclusion, both protection and remoteness were effective in reducing anthropogenic edges and fragmentation, and thus contributed to a high ecological condition in mangroves at a major deforestation hotspot.

Highlights

The extensive human transformation of the biosphere imposes new challenges for the conservation of tropical forests [1] including mangroves [2]
Mean diameter at breast height (DBH), and IVI per species, and percent presence of gastropods were considered as indicators of ecological condition of each transect within each context
Peri-urban mangroves were distinctively fragmented as demonstrated by long edges and high density of patches, Rural mangroves were characterized by long edges surrounded by pastures, and both protected and wild mangroves were dominated by large patches

Summary

Introduction

The extensive human transformation of the biosphere imposes new challenges for the conservation of tropical forests [1] including mangroves [2]. The plethora of human-transformed biomes or anthromes (sensu [3,4]) suggests that conservation of the natural capital may take place under different spatial contexts observed across the continuum from peri-urban and rural landscapes to remote wilderness areas [1,5]. Along this gradient, different land-tenure contexts are observed in public and private lands, imposing different threats to conservation targets. Tropical conservation biologists must learn from the new opportunities offered by the anthropogenic landscapes, moving away from the paradigm of study sites and conservation reserves in isolation from human influences [9,10]

Methods

Results

Conclusion