Rapid Losses of Surface Elevation following Tree Girdling and Cutting in Tropical Mangroves

Lang'at, Joseph Kipkorir Sigi; Kairo, James Gitundu; Mencuccini, Maurizio; Bouillon, Steven; Skov, Martin W.; Waldron, Susan; Huxham, Mark

doi:10.1371/journal.pone.0107868

Cited by 80 publications

(65 citation statements)

References 36 publications

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“…Although, high rates of CO 2 emissions are expected when sediments are exposed to more oxic conditions as occurs with the construction of aquaculture ponds (Kauffman et al, 2014), forest mortality without sediment disturbance gave equivalently high estimates of CO 2 emissions (e.g., Cahoon et al, 2003;Sidik and Lovelock, 2013;Lang'at et al, 2014) that often exceeded the model estimates even at α = 1. High rates of CO 2 emissions in converted mangrove ecosystems may reflect the importance of additional factors that stimulate carbon remineralization under disturbed conditions (e.g., Bianchi, 2011, discussed below).…”

Section: Discussionmentioning

confidence: 95%

“…For example, drainage of peat deposits results in exposure of sediment organic matter to concentrations of oxygen sufficient to stimulate rapid decomposition (Couwenberg et al, 2010). The clearing of mangroves (without excavation) results in CO 2 emissions from sediments probably due to changes in both the structure of sediments and microbial processes as roots die and redox conditions and nutrient availability changes (Lovelock et al, 2011;Lang'at et al, 2014). Excavation of mangrove and tidal marsh sediments to construct ponds for aquaculture may result in high initial emissions as a larger portion of the sediment carbon may be exposed to air (Kauffman et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

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Modeled CO2 Emissions from Coastal Wetland Transitions to Other Land Uses: Tidal Marshes, Mangrove Forests, and Seagrass Beds

2017

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The sediments of coastal wetlands contain large stores of carbon which are vulnerable to oxidation once disturbed, resulting in high levels of CO 2 emissions that may be avoided if coastal ecosystems are conserved or restored. We used a simple model to estimate CO 2 emissions from mangrove forests, seagrass beds, and tidal marshes based on known decomposition rates for organic matter in these ecosystems under either oxic or anoxic conditions combined with assumptions of the proportion of sediment carbon being deposited in either oxic or anoxic environments following a disturbance of the habitat. Our model found that over 40 years after disturbance the cumulative CO 2 emitted from tidal marshes, mangrove forests, and seagrass beds were ∼70-80% of the initial carbon stocks in the top meter of the sediment. Comparison of our estimates of CO 2 emissions with empirical studies suggests that (1) assuming 50% of organic material moves to an oxic environment after disturbance gives rise to estimates that are similar to CO 2 emissions reported for tidal marshes; (2) field measurements of CO 2 emissions in disturbed mangrove forests were generally higher than our modeled emissions that assumed 50% of organic matter was deposited in oxic conditions, suggesting higher proportions of organic matter may be exposed to oxic conditions after disturbance in mangrove ecosystems; and (3) the generally low observed rates of CO 2 emissions from disturbed seagrasses compared to our estimates, assuming removal of 50% of the organic matter to oxic environments, suggests that lower proportions may be exposed to oxic conditions in seagrass ecosystems. There are significant gaps in our knowledge of the fate of wetland sediment carbon in the marine environment after disturbance. Greater knowledge of the distribution, form, decomposition, and emission rates of wetland sediment carbon after disturbance would help to improve models.

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Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 99%

Modeled CO2 Emissions from Coastal Wetland Transitions to Other Land Uses: Tidal Marshes, Mangrove Forests, and Seagrass Beds

2017

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“…Our model does not account for long-term and nonlinear feedbacks within the system where elevation deficits may be enhanced or reduced, for example, through episodic high-wave-energy events that cause erosion 24 , degradation of forests 25 , other stochastic events such as intense storms that may alter hydrology or deliver sediment pulses 26 , or changes in ocean circulation that may influence regional rates of SLR 7 . The frequency and intensity of these events are predicted to increase under climate-change scenarios 2 , and all of these factors will influence the length of time before forest submergence and loss.…”

Section: Research Lettermentioning

confidence: 99%

The vulnerability of Indo-Pacific mangrove forests to sea-level rise

Lovelock

Cahoon

Friess

et al. 2015

Nature

647

459

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Sea-level rise can threaten the long-term sustainability of coastal communities and valuable ecosystems such as coral reefs, salt marshes and mangroves. Mangrove forests have the capacity to keep pace with sea-level rise and to avoid inundation through vertical accretion of sediments, which allows them to maintain wetland soil elevations suitable for plant growth. The Indo-Pacific region holds most of the world's mangrove forests, but sediment delivery in this region is declining, owing to anthropogenic activities such as damming of rivers. This decline is of particular concern because the Indo-Pacific region is expected to have variable, but high, rates of future sea-level rise. Here we analyse recent trends in mangrove surface elevation changes across the Indo-Pacific region using data from a network of surface elevation table instruments. We find that sediment availability can enable mangrove forests to maintain rates of soil-surface elevation gain that match or exceed that of sea-level rise, but for 69 per cent of our study sites the current rate of sea-level rise exceeded the soil surface elevation gain. We also present a model based on our field data, which suggests that mangrove forests at sites with low tidal range and low sediment supply could be submerged as early as 2070.

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“…Soil collapse due to deforestation (Krauss et al 2010;Langat et al 2014), the influences of trampling (Kauffman et al 2004), and the absence of a reliable marker in the deep alluvial soils of the sampled mangroves and pastures compounds difficulties in the comparisons of soil properties based upon depth or volume. At a similar depth there is simply more mass of soil in the pastures than in the mangroves.…”

Section: Soil Carbon and Nutrientsmentioning

confidence: 99%

Carbon stocks of mangroves and losses arising from their conversion to cattle pastures in the Pantanos de Centla, Mexico

Kauffman

Trejo

García

et al. 2015

Wetlands Ecol Manage

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The conservation of mangroves and other coastal ''blue carbon'' ecosystems is receiving heightened attention because of recognition of their high ecosystem carbon stocks as well as vast areas undergoing land conversion. However, few studies have paired intact mangroves with degraded sites to determine carbon losses due to land conversion. To address this gap we quantified total ecosystem carbon stocks in mangroves and cattle pastures formed from mangroves in the large wetland complex of the Pantanos de Centla in SE Mexico. The mean total ecosystem carbon stocks of fringe and estuarine tall mangroves was 1358 Mg C/ha. In contrast the mean carbon stocks of cattle pastures was 458 Mg C/ha. Based upon a biomass equivalence of losses from the top 1 m of mangrove soils, the losses in carbon stocks from mangrove conversion are conservatively estimated at 1464 Mg CO 2 e/ha. These losses were 7-fold that of emissions from tropical dry forest to pasture conversion and 3-fold greater than emissions from Amazon forest to pasture conversion. However, we found that limiting ecosystem carbon stocks differences to the surface 1 m or even 2 m soil depth will miss losses that occurred from deeper horizons. Mangrove conversion to other land uses comes at a great cost in terms of greenhouse gas emissions as well losses of other important ecosystem services.

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Rapid Losses of Surface Elevation following Tree Girdling and Cutting in Tropical Mangroves

Cited by 80 publications

References 36 publications

Modeled CO2 Emissions from Coastal Wetland Transitions to Other Land Uses: Tidal Marshes, Mangrove Forests, and Seagrass Beds

Modeled CO2 Emissions from Coastal Wetland Transitions to Other Land Uses: Tidal Marshes, Mangrove Forests, and Seagrass Beds

The vulnerability of Indo-Pacific mangrove forests to sea-level rise

Carbon stocks of mangroves and losses arising from their conversion to cattle pastures in the Pantanos de Centla, Mexico

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