Mangrove ecosystems are some of the most productive in the world, storing carbon at rates as high as tropical rainforests. Although mangroves represent only ~0.4 % of all forest, they contribute ~10% of the carbon that is permanently removed from the atmosphere & locked up by the coastal ocean. Mangroves are also beneficial to stabilising land at coastal margins, particularly during extreme events such as tropical storms & tsunami, and there is evidence that as sea level rises with global warming, mangroves can adjust to mean tidal heights, maintaining this protective role. Furthermore, mangroves are the fundamental basis of the livelihoods of many people in developing countries, providing, for example, fuel wood, building materials & fisheries. An unfortunate consequence of their productivity, however, is that many mangroves have been overexploited & degraded such that they can no longer sustain themselves as forests, and many of the ecosystem services they have provided in the past have now been lost. In other areas, mangroves have been cleared for conversion to permanently flooded fisheries, rice paddies, or for urban development, with the consequence that global mangrove coverage is now 65% of what it was 20 years ago. This trend is continuing.
Payment for ecosystem services (PES) schemes, either through the voluntary sector or through proposed global mechanisms such as REDD (reduced emissions from deforestation and degradation), seek to reduce or reverse the over-exploitation of natural ecosystems by compensating local stakeholders for income forgone and removing (short-term) financial incentives for overexploitation. One of the main directions that PES schemes are taking is to value the carbon stored & locked up by ecosystems in terms of its financial value to actors with a statutory (or voluntary) commitment to reducing carbon emissions. To achieve this, the amount of carbon stored in, or by, an ecosystem is measured, and compared to the carbon stored in, or by, an alternative land use (or degraded version of the same ecosystem). The difference is the ecosystem's carbon value, and this is converted into an equivalent amount of CO2, the greenhouse gas (GHG) most responsible for global warming.
Although methane (CH4) emissions are much lower than CO2 emissions, CH4 is an important GHG because, over 100 years, each molecule produces as much global warming as 23 CO2 molecules; CH4 contributes ~ 20% of the total radiative forcing. CH4 is mainly produced when organic matter (e.g. leaves) is decomposed by micro-organisms living in anaerobic (oxygen-free) conditions such as those found in the guts of ruminants (cows, sheep) and, crucially, in the flooded soils of wetland ecosystems. Globally, emissions from wetlands contributes around 76% of total CH4 emissions, but uncertainties around this figure are large because we do not have a full understanding of how CH4 production and consumption (by bacteria that oxidise CH4 to produce CO2) balance one another in soils that are permanently, regularly or occasionally flooded. Even less is known about how the degradation, or permanent conversion, of wetland ecosystems affects CH4 emissions. For example, do mangrove trees increase CH4 emissions by supplying organic litter to anaerobic soils & providing channels for CH4 transport (arenchyma - used to supply roots with oxygen), or do they reduce (or increase) CH4 emissions by drying out the surface soil (or preventing it drying out) quickly as the tide recedes, thereby changing the rate of CH4 oxidation?
This project will measure the transport of CO2 and CH4 between the atmosphere and mangrove forests at different stages of degradation and restoration, and determine how the balance between these two forms of carbon emission is driven by biological & environmental factors. With this information, this project will provide a more accurate estimate of the GHG mitigation value of mangrove degradation, conversion & restoration.

Potential Impact:
Conserving threatened mangrove ecosystems to maintain ecosystem services is the main non-academic driver behind this project. Through the involvement of the project partners and their links to external organisations, this project has potential to impact on the design and likely success of payment for ecosystem services (PES) schemes designed to achieve this. The NERC/DfID ESPA project, Swaheli Seas, includes a PES demonstration component, Mikoko Pamoja, that will use carbon credits from the voluntary sector to fund mangrove restoration in the Gazi Bay area. This project will refine the value of the carbon offset offered by Mikoko Pamoja by including the effects of altered CH4 emissions.
If the effect of mangrove degradation on CH4 emissions is large, future PES schemes in other regions should be mindful of the potential effects, positive or negative, this has on the carbon sequestration value of mangroves and other wetland ecosystems. Through the project partner in the Kenya Marine and Fisheries Research Institute (KMFRI), it is hoped that this project will feed into 1) Kenya's developing national strategy for REDD/+ (Reduced emission from deforestation/degradation) implementation, helping highlight the importance of mangrove conservation nationally, and 2) the CAMARV project aimed at building capacity for value ecosystem services across East Africa.
In contributing to stakeholders' evidence bases describing the GHG effects of differing land management interventions, this project will strengthen policy makers' efforts to manage and protect ecosystem services, build ecosystem resilience and mitigate further ecosystem degradation in the low-income coastal areas that are likely to be among those that first feel the impacts of global change. By engaging with NERC's Ecosystem Services for Poverty Alleviation (ESPA) and Living With Environmental Change (LWEC) programmes, this project will contribute to a fuller understanding of the ecosystem services provided by coastal forest ecosystems, globally.
The ecosystem services framework for integrating and prioritising tradeoffs between competing land uses is currently informing most approaches to sustainable development and adaptation to a low-carbon future. In general, however, progress by the scientific community in quantifying and monetising ecosystem services is slower than desired by policymakers. Again, this project, seen in the context of its linkage to the Swaheli Seas project, and to the partners' projects on other ecosystem services, will contribute to this progress.
This project is achievable because of the co-operation between the PI, project partners in the UK, and KMFRI. In common with many research organisations in developing countries, limited access to state-of-the-art facilities and to the international scientific community means that many Kenyan scientists do not achieve international recognition. Through this project it is hoped to contribute informally to capacity building among scientists at KMFRI. Although the cost and complexity of eddy covariance systems mean they will not become commonplace in the near future, projects such as this will, to a certain extent, normalise the use of high technology in the context of developing countries.
The post-doc employed on this project will become one of only a few people in the UK with the capability of measuring GHG fluxes by micrometeorological methods. As use of this technique becomes increasingly important in the future, the training in these techniques afforded by this project will greatly enhance his/her skill base and career prospects.
The canopy tower used as an instrument platform during the project will afterwards be offered to the Gazi Women's Mangrove Boardwalk Group (a legally constituted co-operative that operates ecotourism activities in the forest) for use as a canopy observation and bird-watching platform, adding value to their group, and further developing non-use ecosystem services.