CO2 efflux from cleared mangrove peat

Abstract

Background: CO(2) emissions from cleared mangrove areas may be substantial, increasing the costs of continued losses of these ecosystems, particularly in mangroves that have highly organic soils.

Methodology/principal findings: We measured CO(2) efflux from mangrove soils that had been cleared for up to 20 years on the islands of Twin Cays, Belize. We also disturbed these cleared peat soils to assess what disturbance of soils after clearing may have on CO(2) efflux. CO(2) efflux from soils declines from time of clearing from ∼10,600 tonnes km(-2) year(-1) in the first year to 3000 tonnes km(2) year(-1) after 20 years since clearing. Disturbing peat leads to short term increases in CO(2) efflux (27 umol m(-2) s(-1)), but this had returned to baseline levels within 2 days.

Conclusions/significance: Deforesting mangroves that grow on peat soils results in CO(2) emissions that are comparable to rates estimated for peat collapse in other tropical ecosystems. Preventing deforestation presents an opportunity for countries to benefit from carbon payments for preservation of threatened carbon stocks.

Figure 1. Variation in CO₂ efflux from peat soils over the time since the mangrove forest was cleared from Twin Cays Belize.

The fitted line is of the form: Log CO₂ Efflux  =  a x exp (-b x time) where a = 0.712 and b = 0.656; R² = 0.51. The model is significant: F_1,30 = 40.4988, P<0.0001.

Figure 2. CO₂ efflux from peat soils that were cleared of forest (cleared 8 months) where peat was disturbed by cutting blocks from the soils (disturbed) and two days after the blocks of peat were cut (2 days post-disturbance).

There was a significant effect of the disturbance treatment (F_2,15 = 25.37, P<0.0001) but after two days there was no significant difference in soil CO₂ efflux between disturbed and undisturbed samples.