Mangrove forests have experienced a rapid decline. However, the rate of loss has decreased in recent years due to enhanced conservation and nature regeneration. The dynamics of mangrove forests in Panama have not been monitored since the year 2000, despite a significant loss during the 1980s. The objectives of our study were to quantify changes in mangrove cover and identify the dominant drivers of change in Parita Bay, Panama. Temporal changes in mangrove cover and the Normalized Difference Vegetation Index (NDVI) were determined using the supervised classification method on Landsat satellite images from 1987 to 2019. We identified a 4.7% increase in the mangrove area of Parita Bay during the 32 years; the mangrove forests were also considered healthy as reflected by high NDVI values. However, the conversion of mangroves to other land cover types resulted in a 1.26% decline in mangrove cover from 1987 to 1998. Moreover, the area of aquaculture and saltpans almost doubled during this period. During the following two decades, the conversion of other land cover classes (water, other vegetation, and bare soil) increased the mangrove area by 6%, and the annual rate of increase was greater during the second decade (0.43% year⁻¹). From 2009 to 2019, mangroves declined at an annual rate of 0.11% in protected areas and increased at an annual rate of 0.50% in unprotected areas. Despite the regeneration potential of mangrove forests, our study highlights the need to continually manage and protect mangrove forests in order to facilitate their expansion in Parita Bay.

(1) Background: Down-regulation of photosynthesis has been commonly reported in elevated CO₂ (eCO₂) experiments and is accompanied by a reduction of leaf nitrogen (N) concentration. Decreased N concentrations in plant tissues under eCO₂ can be attributed to an increase in nonstructural carbohydrate (NSC) and are possibly related to N availability. (2) Methods: To examine whether the reduction of leaf N concentration under eCO₂ is related to N availability, we investigated understory Fraxinus rhynchophylla seedlings grown under three different CO₂ conditions (ambient, 400 ppm [aCO₂]; ambient × 1.4, 560 ppm [eCO₂1.4]; and ambient × 1.8, 720 ppm [eCO₂1.8]) and three different N concentrations for 2 years. (3) Results: Leaf and stem biomass did not change under eCO₂ conditions, whereas leaf production and stem and branch biomass were increased by N fertilization. Unlike biomass, the light-saturated photosynthetic rate and photosynthetic N-use efficiency (PNUE) increased under eCO₂ conditions. However, leaf N, Rubisco, and chlorophyll decreased under eCO₂ conditions in both N-fertilized and unfertilized treatments. Contrary to the previous studies, leaf NSC decreased under eCO₂ conditions. Unlike leaf N concentration, N concentration of the stem under eCO₂ conditions was higher than that under ambient CO₂ (4). Conclusions: Leaf N concentration was not reduced by NSC under eCO₂ conditions in the understory, and unlike other organs, leaf N concentration might be reduced due to increased PNUE.