Table 1.

Examples of gains and losses for BC stocks with a range of climate change factors

Ecosystem	Sea level rise	Extreme storms	Higher temperatures	Extra CO2	Altered precipitation
Mangrove	Landward expansion increases area and C stocks Losses of low intertidal forests and coastal squeeze could reduce C stocks Increasing accommodation space increases C sequestration	Canopy damage, reduced recruitment and soil subsidence resulting in losses of C stocks Soil elevation gains due to sediment deposition increasing C stocks and, reducing effects of sea level rise	Minimal impacts anticipated, although increased decomposition of soil C possible Poleward spread of mangrove forests at expense of tidal marshes increases C stocks Change in dominant species could influence C sequestration	An increase in atmospheric CO2 benefits plant productivity of some species which could alter C stocks	Canopy dieback due to drought Losses of C stocks due to remineralization and reduced productivity Increased rainfall may result in increased productivity and C sequestration
Tidal Marsh	Landward expansion increased area and C stocks Losses of low intertidal marsh and coastal squeeze could reduce C stocks Increasing accommodation space increases C sequestration	Loss of marsh area and C stocks Enhanced sedimentation and soil elevation increasing C stocks and, reducing effects of sea level rise	Increased temperatures may increase decomposition of soil organic matter, but offset by increased productivity of tidal marsh vegetation Poleward expansion of mangroves will replace tidal marsh and increase C storage Poleward expansion of bioturbators, may decrease soil C stocks	An increase in atmospheric CO2 benefits plant productivity of some species which could alter C stocks	Reduced above and belowground production due to drought reducing C sequestration Possible losses of C stocks due to remineralization Impact could be greater in areas that already have scarce or variable rainfall
Seagrass	Loss of deep water seagrass Landward migration in areas where seawater floods the land (into mangrove or tidal marsh ecosystem)	Some extreme storms cause the erosion of seagrasses and loss of seagrass C stocks but some seagrass species are resistant to these major events Flood events associated with extreme rainfall may result in mortality, but could also increase sediment accretion and C sequestration	Thermal die-offs leading to losses of C stocks Species turnover Colonization of new poleward regions Increased productivity	An increase in dissolved inorganic C benefits plant productivity increasing C stocks Ocean acidification leads to loss of seagrass biodiversity, decreasing C stocks	Most seagrasses are tolerant of acute low salinity events associated with high rainfall, but some are negatively affected and potential interactions with disease may lead to losses of C stocks Reduced rainfall increases light availability which increases productivity and C sequestration
Seaweed	Loss of deep water seaweeds  Seaweeds are expected to colonise hard substrata that become flooded, increasing C stocks	Reduces seaweed cover, but could lead to sequestration of C stocks as detritus sinks	Major retraction in kelp forest C stores at non-polar range edges; Expected expansion at polar range edges.	Increased biomass and productivity of kelp where water temperatures remain cool enough	Little effect overall Regional effects on seaweed flora in areas with high land run off/rivers

Bold text indicate potential positive effects on BC stocks, italic text indicate negative effects with roman text indicating where effects could be positive or negative