Print PageAlthough mangrove forests are generally regarded as highly threatened,some studies have shown that mangrove canopies in the Pacific coast ofMexico have been increasing in recent decades. We investigated the possiblecauses driving this reported mangrove expansion.
We used 50-year-old aerial photographs and 24-year-old satelliteimages to compare long-term vegetation change, surveyed a coastal vegetationtransect to analyse flooding levels, compiled six decades of tidal and oceanographicinformation, as well as hurricane data to analyse changes in stormfrequency or sea-level conditions, and used isotopic analysis to date the age oftrees along the gradient.
Results/Conclusions
A significant increase in mangrove cover has occurred in backwatersof the lagoons during the last 40 years, and especially during the El Nin˜ oanomalies of the 1980s and 1990s, while at the same time the mangrove fringehas been receding.
The observed change can be attributed to the combined action ofthe warm surface waters of El Nin˜ o events and sea-level rise. Jointly, these twoeffects are sufficient to flood large areas of previously non-flooded salt flats,dispersing mangrove seedlings inland. The inland expansion of mangroves, however,does not ease conservation concerns, as it is the seaward fringes, and not theinland margins, that provide the most valuable environmental services for fisheriesand coastal protection.
