The basic idea

The CurFEW conceptual framework centres on a coupled climate–hydrology–ecosystem–biogeochemistry feedback. The Indian Ocean Dipole (IOD) acts as a large-scale climate driver. In its positive phase, anomalously warm sea surface temperatures in the western Indian Ocean enhance convection, leading to increased precipitation over eastern Africa. This anomalous rainfall is stored within river catchments and lakes, which subsequently release water, generating anomalous discharge and flooding regimes.

These hydrological anomalies propagate into wetlands, altering:

• the extent and duration of inundation (permanent vs seasonal)

• hydrological connectivity

• and consequently vegetation composition and spatial distribution

Wetland vegetation plays a dual role in methane cycling:

1. • Substrate supply plant biomass (particularly senesced material) forms the organic carbon pool that fuels anaerobic microbial metabolism (methanogenesis). At the same time, methanotrophic microbes can oxidise methane, introducing a competing sink.

   • Transport pathway modulation Methane produced in saturated soils and sediments reaches the atmosphere via: diffusion through the water column; ebullition (bubble release); and plant-mediated transport, which can dominate in certain systems

In eastern Africa, macrophytes such as Cyperus papyrus and Phragmites spp. act as aerenchymatous conduits, effectively short-circuiting oxidation pathways by transporting methane directly from sediment to atmosphere.

Satellite observations indicate that eastern African wetlands constitute a major global methane emission hotspot, with the Sudd wetland complex identified as a particularly significant source. Interannual variability in its inundation extent has been linked to a substantial fraction of recent global atmospheric methane growth.

The final component is the prospective climate feedback:

• Climate model projections suggest that greenhouse-gas-driven warming may increase the frequency and/or intensity of positive IOD-like conditions.

• This would enhance precipitation, flooding, and wetland expansion or persistence.

• In turn, this amplifies methane emissions via the mechanisms described above.

This defines a biogeochemical positive feedback loop:

Warming >> stronger/more frequent positive IOD >> increased wetland inundation >> enhanced methane emissions >> additional warming

However, the magnitude and stability of this feedback remain uncertain, due to nonlinear interactions among hydrology, vegetation dynamics, and microbial processes.

By acquiring new observations that constrain (i) the response of catchment-scale hydrodynamics to anomalous rainfall, (ii) the propagation of these hydrological changes into downstream wetland inundation, and (iii) the resulting impacts on vegetation biomass, composition, and organic matter inputs, we can substantially improve process-level understanding of the controls on wetland methane cycling.

This integrated, multi-scale understanding enables a more mechanistic representation of how hydrological variability is translated into changes in methane emissions—both under present-day conditions and under future climate scenarios.

While even the basic idea is actually quite complex -- involving atmospheric physics and chemistry, hydrological dynamics, ecology, and microbiology -- we have boiled it down to addressing four science questions: