Table 3.

Potential annual CO₂ emissions from loss of Australian vegetated coastal ecosystems and economic valuation

a
Ecosystem	Total stock (Soil + Biomass) (Tg C)	Habitat loss per year (ha year−1)	C at risk of remineralization (Tg C year−1)	Potential CO2 emissions (Tg CO2-e year−1)	Economic value of CO2 emissions per year ($10 t CO2−1) (106 US$)
Tidal marsh	212–237	413–460	0.036–0.040	0.13–0.15	1.3–1.5
Mangrove	131–415	99–315	0.019–0.059	0.07–0.22	0.7–2.2
Seagrass	778–1,073	9,257–12,772	0.53–0.73	1.9–2.7	19–27
Total	1121–1725	9769–13,547	0.58–0.83	2.1–3.1	21–30

b
Ecosystem	Sequestration rates in Australia (Tg C year−1)	Habitat loss per year (ha year−1)	Lack of C sequestration (Gg C year−1)	Potential lack of CO2 sequestration (Gg CO2-e year−1)	Economic value of lack of CO2 sequestration per year ($10 t CO2−1) (106 US$)
Tidal marsh	0.48–0.53	413–460	0.16–0.18	0.58–0.65	0.0058–0.0065
Mangrove	0.4–1.4	99–315	0.13–0.40	0.46–1.46	0.0046–0.015
Seagrass	2.5–3.5	9,257–12,772	3.3–4.6	12.2–16.9	0.12–0.17
Total	3.5–5.5	9,769–13,547	3.6–5.2	13.3–19.0	0.13–0.19

a: Potential gross annual emissions (Tg CO₂-e year^-1) from aboveground biomass and soils as a result of the decline in vegetated coastal ecosystems extent in Australia (0.03% year^-1 for tidal marshes and mangroves, and 0.1% year^-1 for seagrasses). Emission estimates assume that 50% of organic carbon (C) stocks in aboveground biomass and in the top meter of soil deposits are remineralized after ecosystem loss (at a rate of 0.183 year^{−1 46})

b: Potential annual loss of CO₂ sequestration capacity in blue carbon soils as a result of current losses in the extent of vegetated coastal ecosystems in Australia, assuming that soil C accretion does not occur after ecosystem loss. Carbon trading price of US$ 10 per ton of CO₂. Economic value is expressed in 10⁶ US$