Understanding Drivers

Polder in the Netherlands

The scientific challenge of this theme is to understand the complex interactions between physical, biological and chemical processes, and human interventions that affect subsidence and loss of ecosystem services.

Subsidence

There are numerous drivers of subsidence, such as natural sediment compaction, sediment loading, extraction of natural resources, tectonics, isostasy, groundwater level fluctuations, biogeochemical processes, land use and sediment starvation due to upstream trapping. Human forcing of subsidence, such as groundwater extraction and construction of dikes and dams, is influenced by socio-economic conditions and the governance system.

Ecosystem services

Subsiding land in deltas potentially affects ecosystem functioning by degradation or loss of agricultural soils, reduced freshwater supply by intrusion of salt water, deterioration of water quality by eutrophication, loss of biodiversity and loss of coastal protection zones. Also, groundwater level lowering in peat soils causes subsidence due to peat oxidation, which leads to considerable greenhouse gas emissions thereby generating a positive feedback on climate change, as the expectations are that climate change will further accelerate peat oxidation and subsidence under prolonged periods of drought and higher temperatures.

In Future Deltas it is our aim to unravel and quantify the different contributors to subsidence in different deltas, and to understand how they relate to loss of ecosystem services under a changing climate.