Analysis of relationship between the meteorological and hydrological droughts and biomass change of mangrove forests in the Gwatr Port over a 34-year period

The analysis of changes in mangrove forests production capacity and its relation to the drought periods can provide valuable information on the vulnerability of these ecosystems to the adverse effects of climate change. This study investigates the effect of long-term drought occurrences on the production capacity of the mangrove forests in the Gwatr Port in the Sistan and Baluchestan province. To do this, by recording the diameter at breast height and calculating the above and below ground biomass in the sample plots and analyzing the relationship between these characteristics with the Landsat satellite images, 34-year time series (1986-2019) mangrove biomass were mapped and the relationship between biomass variations and changes in meteorological drought (measured using SPI) and hydrological drought (measured using SSFI) was analyzed. The results showed that the above and below ground biomasses follows the trends of change in the severity of meteorological and hydrological droughts during the 34-year period such that in the wet season before 1998, mangrove biodiversity increased, and then with long-term droughts after 1998, the decline in biomass continued until the end of the period. The coincidence between biomass changes and SPI and SSFI variations resulted in a high correlation between mangrove biomass variations with changes in the severity of meteorological and hydrological droughts (correlation coefficients greater than 0.82). The results of this study can be used for developing climate change adaptation programs and for the restoration and development of mangrove forests in the Sistan and Baluchestan province.