Global forest biodiversity is in decline. However, studies assessing long-term change in forest biodiversity often focus on changes in species richness, and somewhat little attention has been given to the changes in species evenness. Using Bangladesh Forest Department’s inventory plots data for the period of 1986 – 2014, here we examine the patterns of long-term changes in species richness and evenness of Sundarbans mangrove forest, which is the largest single tract of mangrove forest in the world.
Results/Conclusions
Our results indicate a marked decrease in species evenness in the Sundarbans mangrove over the last two decades (that is, the forest has become more uneven). Interestingly, we did not find any significant change in species richness. These results indicate that species’ relative abundance, which governs species evenness, has changed without loss of any species. Our species level analysis indicate that the temporal trends of decreasing evenness is associated with increasing dominance of the salt tolerant species, as the rising sea level over the last two decades has led to significant raise in salinity in this forest. Based on our results, that no change in richness but significant decrease in evenness, we conclude that species evenness is a more useful indicator than species richness to detect long-term change in forest biodiversity.