Mass mortality of black mangrove ( Avicennia germinans ) has reshaped extensive areas of Estero Pargo, a tidal channel in Laguna de Términos, southeastern Mexico. To identify the factors and mechanisms driving this die-back and to evaluate recovery potential, we integrated three complementary approaches: (i) a spatial gradient analysis along three transects spanning healthy fringe forest, transition stands, and complete die-back; (ii) field experiments testing the effects of water-level manipulation, herbivory exclusion and seedling provenance on Avicennia germinans seedling performance; and (iii) long-term monitoring (2012–2016) of groundwater level, interstitial salinity, soil redox potential and canopy condition. Dry-season hydrological disconnection lowered the water table to more than 30 cm below the soil surface, which coincided with extreme interstitial hypersalinity (> 70‰) and strongly reducing soil conditions (<–100 mV). These thresholds initiated widespread mortality and set in motion reinforcing feedbacks (canopy loss, increased soil heating and salt accumulation) that accelerated ecosystem degradation. Seedling experiments confirmed that hydrological stress is the primary barrier to recovery: survival and growth dropped sharply in die-back zones but improved markedly when seedlings were placed on elevated substrates that reduced waterlogging and salinity. Around surviving adult trees, microenvironmental measurements showed lower salinity, higher redox potential and more moderate soil moisture, producing refuges in which seedling survival exceeded 80%. These remnant trees act as nucleation centers for potential regeneration, even as surrounding areas shift toward more permanent hypersaline flats. Effective restoration in Estero Pargo, and in comparable systems facing increasing climatic stress, will depend on restoring hydrological connectivity, modifying microtopography and protecting surviving trees.
Meléndez et al. (Thu,) studied this question.