Death and Regeneration of an Amazonian Mangrove Forest by Anthropic and Natural Forces

Author(s)

Cardenas, Sergio M. M. ; Cohen, Marcelo C. L. ; Ruiz, Diana P. C. ; Souza, Adriana V. ; Gomez-Neita, Juan. S. ; Pessenda, Luiz C. R. ; Culligan, Nicholas

• Document type: Journal article
• Source: REMOTE SENSING; v. 14, n. 24, p. 25-pg., 2022-12-01.

Abstract

The Amazon Macrotidal Mangrove Coast contains the most extensive and continuous mangrove belt globally, occupying an area of similar to 6500 km(2) and accounting for 4.2% of global mangroves. The tallest and densest mangrove forests in the Amazon occur on the Braganca Peninsula. However, road construction that occurred in 1973 caused significant mangrove degradation in the area. A spatial-temporal analysis (1986-2019) based on optical, Synthetic Aperture Radar (SAR), drone images, and altimetric data obtained by photogrammetry and validated by a topographic survey were carried out to understand how the construction of a road led to the death of mangroves. The topographic data suggested that this road altered the hydrodynamical flow, damming tidal waters. This process killed at least 4.3 km(2) of mangrove trees. Nevertheless, due to natural mangrove recolonization, the area exhibiting degraded mangrove health decreased to similar to 2.8 km(2) in 2003 and similar to 0.73 km(2) in 2019. Climatic extreme events such as "El Nino" and "La Nina" had ephemeral control over the mangrove degradation/regeneration. In contrast, the relative sea-level rise during the last several decades caused long-term mangrove recolonization, expanding mangrove areas from lower to higher tidal flats. Permanently flooded depressions in the study area, created by the altered hydrodynamical flow due to the road, are unlikely to be recolonized by mangroves unless connections are re-established between these depressions with drainage on the Caete estuary through pipes or bridges to prevent water accumulation between the road and depressions. To minimize impacts on mangroves, this road should have initially been designed to cross mangrove areas on the highest tidal flats and to skirt the channel headwaters to avoid interruption of regular tidal flow. (AU)

• FAPESP's process: 20/13715-1 - Dynamics of American mangroves at austral and boreal limits on secular and decadal scales
• Grantee: Luiz Carlos Ruiz Pessenda
• Support Opportunities: Regular Research Grants