Changing Land-Atmosphere Feedbacks in Tropical African Wetlands

Lead Research Organisation: NERC CEH (Up to 30.11.2019)
Department Name: Harding


The primary aim of the proposed research is to quantify the feedbacks between tropical African wetlands and climate. We will do this by implementing a dynamic wetland inundation scheme in an Earth system model, and test this model against soil moisture, cloud cover and methane (CH4) concentration data obtained through remote Earth observation. Our research will address the following key questions: How does the presence of tropical wetlands affect rainfall at the regional scale? Are wetland emissions of CH4 strongly dependent on seasonal and inter-annual hydrological variability? How will wetland seasonality and associated emissions of CH4 alter under environmental and climate change scenarios? The research proposed here will build on recent developments in land-surface modelling and Earth observation to incorporate detailed hydrological understanding of wetland function into climate models. We will combine novel satellite Earth observations, field measurements, and a new dynamical representation of wetland inundation to add greatly to our understanding of the importance of wetlands in the Earth system under scenarios of environmental change. Wetlands interact with the climate system in two ways. First, they govern the fluxes of heat and water at the land-surface, which can feed back on rainfall at the local and regional scales. Second, wetlands form a key link between the hydrological and carbon cycles, via anoxic degradation of organic matter to release CH4. It is estimated that wetland CH4 emissions represent 20-40% of the global CH4 budget making wetlands the largest single natural source of atmospheric CH4. Both CH4 and hydrological feedbacks are expected to be most active in the tropics, yet it is here that CH4 fluxes are least well quantified. These concerns are amplified in the context of climate change: warming resulting from a doubling of atmospheric CO2 concentrations will likely lead to a 78% increase in wetland emissions of CH4, most of which will come from tropical regions. Moreover, recent rapid increases in global CH4 concentrations have recently been attributed to natural variations in the extent of flooding in tropical wetlands. The lack of robust information on the ways in which tropical wetlands modulate fluxes of heat, water and trace gases to the atmosphere currently hampers progress in predicting the effects of global environmental change. We urgently need a better understanding of how wetlands function in the Earth system.
Description 1. A model to calculate inland flooding at large-scales for use in climate modelling applications
2. Supporting datasets for use with the Met Office Hadley Centre Unified Model system
3. Understanding of the effects of surface-water inundation on land-atmosphere feedbacks
4. Use of Earth observation data to constrain methane cycle in tropical African wetlands
Exploitation Route Results and outputs are currently being used to support follow-on studies funded by NERC (FCFA) and DfID (IWSP).
Sectors Environment

Description Leverhulme
Amount £20,000 (GBP)
Organisation The Leverhulme Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2015 
End 09/2018
Description REACH
Amount £15,000,000 (GBP)
Organisation Government of the UK 
Department Department for International Development (DfID)
Sector Public
Country United Kingdom
Start 09/2015 
End 09/2022
Description UKSA IPP
Amount £2,000,000 (GBP)
Organisation UK Space Agency 
Sector Public
Country United Kingdom
Start 03/2016 
End 03/2019
Title RFM in JULES 
Description River routing model (RFM) for use in Joint UK Land Environment Simulator (JULES) developed in collaboration with UK Met Office 
Type Of Material Computer model/algorithm 
Year Produced 2015 
Provided To Others? Yes  
Impact Contributes to UK Environmental Prediction capability 
Title Topographic Index global layer 
Description Here we present new, high-resolution parameter maps of the topographic index for all ice-free land pixels calculated from hydrologically-conditioned HydroSHEDS data using the GA2 algorithm ('GRIDATB 2'). At 15 arc-sec resolution, these layers are four times finer than the resolution of the previously best-available topographic index layers, the Compound Topographic Index of HYDRO1k (CTI). 
Type Of Material Database/Collection of data 
Year Produced 2014 
Provided To Others? Yes  
Impact Increasing the resolution at which global hydrological simulations are carried out will have many benefits including the more realistic representation of processes currently at subgrid resolution and, ultimately, better weather and inundation prediction. Methane production in wetlands, for example, is critically dependent on the level of the water table, models of which are in turn dependent on accurate representation of the topography, therefore higher resolution simulations involving improved topographic index values should of necessity improve the representation of wetland fluxes of heat, water and trace gases to the atmosphere and overall estimates of methane release. Data have been provided to: The Gordon & Betty Moore Foundation Andes-Amazon Project (coordinated by Prof. Moorcroft, Harvard Univ.) The Joint Research Centre (JRC), Ispra, Italy The Department of Life Sciences, Imperial College London Two separate researchers at the Max Planck Institute for Biogeochemistry (BGC-Jena) The Norwegian Forest and Landscape Institute (Skog og Landskap), Ås, Norway The BRIDGE Project, University of Bristol and The Water Resources & Coastal Engineering Laboratory, Technical University of Crete (TUC) 
Description Met Office 
Organisation Meteorological Office UK
Country United Kingdom 
Sector Academic/University 
PI Contribution Collaborative work to implement river routing scheme in Met Office Unified Model
Collaborator Contribution Collaborative work to implement river routing scheme in Met Office Unified Model
Impact This work is ongoing and will result in the capability to predict river flows in the Met Office Unified Model
Start Year 2012
Description Oxford Water Network 
Organisation University of Cape Town
Country South Africa 
Sector Academic/University 
PI Contribution We have participated in this initiative and it has resulted in two successful research proposals, one to EPSRC and another to NERC.
Start Year 2012
Description DFID-REACH Panellist: Water Security in Africa 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact 150 people from Ethiopia, Kenya, Bangladesh attended a conference of which this panel was a component
Year(s) Of Engagement Activity 2019