Carbon reserves in deltaic mangroves of the Colombian Pacific across different disturbance degrees

Abstract

Mangrove forests occupy less than 1% of tropical forest areas, but account for approximately 3% of global tropical forest carbon sequestration and act as a natural atmospheric CO2 sequestration mechanism, which gives them an important role in climate change mitigation. However, different anthropogenic disturbances continue to negatively impact the structure and function of mangrove ecosystems; therefore, it is important to investigate the effect of specific anthropogenic alterations on the capacity of mangroves to store carbon. The present study aimed to test the hypothesis of a direct relationship between the degree of anthropogenic intervention and the reduction of mangrove carbon stocks. Eight edge forest types with different degrees of anthropogenic intervention and multiple uses were selected. Six 100 m2 plots were established in each forest to determine its structure and evaluate the concentration of sedimentary organic carbon and biomass. The anthropogenic disturbance index (ADI) was used to quantify the degree of specific disturbances in the studied forests. The results supported the proposed hypothesis, showing that the mangroves with the highest anthropogenic disturbance measured through the ADI registered the lowest values in blue carbon. However, it is evident that in addition to anthropogenic disturbances, impacts such as coastal erosion pose a very important threat to some of these forests. Estimated organic carbon losses in the study area were between 8.4% and 49.3%, corresponding to 158 and 929 Mg CO2 eq ha−1, respectively. Logging is one of the main disturbances that affects forests differently according to their structural development. Forests with higher structural development are subject to greater pressure. Carbon losses from logging are not only reflected in aboveground carbon, but are also evident in sedimentary carbon.