# Impacts of Climate Change on Blue Carbon Stocks and Fluxes in Mangrove Forests
## 3 Climate Change Impacts
### Rising Temperatures, Increased Storms, Extreme Weather Events, and Precipitation Changes
The increased occurrence of such events is having a dramatic impact on mangroves, especially more frequent episodes of mass mortality [66; 67; 68; 69; 70; 71]. The best example of such occurrences is the massive dieback of mangroves in the Gulf of Carpentaria, Australia, where 6-10% of the forests died back along 1000 km of coastline during summer 2015-2016 [66]. The onset of the dieback is coincident with unprecedented high temperatures, low rainfall, and the lack of a normal monsoon. Figure 2: Potential changes in mangrove carbon stocks for two SLR scenarios, (**A,B**) RCP8.5 (high CO\({}_{2}\) emissions) and (**C,D**) RCP4.5 (lower CO\({}_{2}\) emissions) and for a low coastal squeeze–high adaptation scenario (**A,C**) and high coastal squeeze–low adaptation scenario (**B,D**). Warm colors indicate net losses and cool colors indicate net gains. Source: [58]. Open access under the CC By-NC-ND license 4.0. Contributing to the mass mortality was an unusually lengthy severe drought coupled with a temporary drop in sea level associated with the 2015-2016 El Nino [67]. The dieback had severe consequences for ecosystem functioning and structure, including blue carbon stocks and cycling [68; 69; 70]. Mass mortality of mangroves in the Gulf of Carpentaria resulted in a decline in export of carbon and alkalinity to the adjacent coastal ocean [68], large losses of carbon stock [69], and a weakening of greenhouse gas cycling with a lowering of both source/sink cycles in dry years [70]. The effects of cyclones are similar in terms of mangrove carbon cycling as impacts include broken trees, canopy gaps, large amounts of downed woody debris, and irregular surface soil distributions with alternating areas of smothering and scouring of the forest floor as well as greater soil anoxia [71]. [PERSON] and [PERSON] [71] estimated that forest mortality due to cyclone damage globally averages 40% (range: 13-67%). In the Florida Everglades where mangroves are frequently damaged by cyclones, carbon losses (soil plus biomass) can be severe [72]. Furthermore, short-statured forests often develop in cyclone-prone areas, which translates in more resilient stands but with reduced aboveground biomass carbon stocks [73]. Assuming no peat collapse, soil carbon stock losses will likely be less than biomass losses [74]. Although recovery is often rapid post-cyclone, such carbon increases must be counterbalanced against the cyclone losses. Rainfall patterns in the subtropics and tropics are changing, with weaker monsoons but more frequent and intense rainfall in parts of Africa, south Asia, and Southeast Asia [52]. High rainfall ordinarily leads to more luxurian and productive mangroves and thus more blue carbon as, globally, mangrove canopy height is closely linked to rainfall as well as temperature and cyclone frequency [73]. The opposite of course is true as arid-zone mangroves are expected receive less rainfall [52]. Rainfall thresholds have been identified for mangrove range limits in western North America, western Gulf of Mexico, western South America, Western Australia, the Middle East, northwest Africa, east central Africa, and west central Africa [75].