Flooding Impacts on Ecosystems in the UK

The latest UK State of the Climate Report, published on 30 July 2020 by the International Journal of Climatology, contains several indicators that the UK climate is getting wetter, illustrating that total rainfalls over a five-day period were 4% higher during the most recent decade (2008–2017), compared to the period between 1961–1990. The amount of rain from extremely wet days has increased by 17% when compared to the same time periods. In addition, there is a slight increase in the longest sequence of consecutive wet days for the UK.

The winters of 2013–2014 and 2015–2016 have been the two wettest on record, with widespread impacts – including flooding – during both seasons. A Met Office study shows that an extended period of extreme winter rainfall in the UK, similar to that seen in the winter of 2013–2014, is now about seven times more likely due to human-induced climate change. Past trends show that winter rainfall has intensified and increasingly occurred in clustered events.

These factors were seen in the recent (December 2015) Storm Desmond in Cumbria, which researchers alleged was ‘the most extreme flooding in 600 years’, with larger sedimentary deposits in nearby streams and hills indicating that recent flooding was much more extreme in recent years. During this storm, more than 341mm (13ins) of rain fell in parts of Cumbria in just 24 hours.

The increase of flooding events in the UK not only impacts humans, but also affects wildlife and disrupts entire ecosystems. Coastal areas are further at risk from the combination of storm surges and increased rainfall and river flow, which results in ‘compound flooding’.

Climate change is having an impact on many levels, not least on many vital ecosystems, thus further degrading and destroying the biodiversity we rely on. Flood waters not only threaten to overwhelm fragile ecosystems, but the resulting soil erosion further contributes to habitat and biodiversity loss.

Disruption to species caused by changing weather patterns

Fluctuations in seasonal and weather patterns negatively impact flora and fauna alike, resulting in further degradation of entire ecosystems. This is something we absolutely cannot afford to remain indifferent to or allow to continue, as we rely on having healthy ecosystems – including those underground or in areas we cannot easily observe – to support a variety of species. These, in turn, are vital to our own survival as a species.

Even the merest shift in the timing of seasonal flooding will disrupt lifecycle stages of various flora and fauna far more than if had they occurred in line with normal seasonal patterns. This applies equally to underground habitats, which are rarely investigated or understood, because they remain out of sight.

For example, any disruption to the normal lifecycles of insects and fungi will have far-reaching impacts on wider, more visible ecosystems. The lifecycles of fungi are vital to the lifecycles of other species, and so have a key role in sustaining the overall health of ecosystems. This includes the many species of pollinating insects that nest on or below the ground, and which are responsible for creating human food supplies.

Impacts on estuaries

Flooding mixed with pollution is another negative impact on marine ecosystems, such as estuarine, river, wetland and coastal habitats. Flooding increases the flow of polluted drain water from roads and agricultural land. These can destroy fragile ecosystems in marsh and wetland areas, including the streams and rivers that later feed into seas via estuaries.

Changes in levels of salinity in estuaries are also likely to affect the diversity and distribution of fauna species. A projected increase in the salinity range in estuarine habitats may further reduce biodiversity – for example, of some species found in the Thames Estuary (Attrill, 2002).

Species found in the Thames tidal basin include 125 types of fish (bream, perch, pike, roach, dace, ruffe, barbel, native and non-native carp, chub and gudgeon, among others), according to Ian Tokelove of the London Wildlife Trust, and mammals such as harbour seals, grey seals, harbour porpoises and bottlenose dolphins. Key Thames Tidal Estuary bird species include avocet, black-tailed godwits, dark-bellied brent geese, dunlins, lapwings, gadwalls, grey plovers, oystercatchers, redshanks, shelducks, shovelers and knots, among others).

Estuarine habitats are biologically important and are often very rich in biodiversity, especially in the UK, where plentiful estuarine habitats support many unique and rare species. Estuarine habitats include important nursery areas for commercial fishery species, as well as feeding and breeding areas for terrestrial populations, such as birds (Sharps et al., 2015). UK estuaries are also significant process centres for coastal hydrological, biogeochemical and biological cycles; their biological productivity rivals those of tropical rainforests and coral reefs (Cai, 2011).

Impacts to coastal nature reserves

More than a third of the UK’s national nature reserves are in coastal areas and, like much of the coast, suffer threats from increased erosion, coastal squeeze, habitat loss and saline intrusion, making the fulfilment of some of the government’s current targets for biodiversity difficult or impossible in the long term.

At a single UK nature reserve – the Backwarden site of special scientific interest (SSSI) in Essex – 29%–49% of plant species show a trend of decreasing (including three species identified as a conservation priority by the site manager). However, in all such studies, the observations depend on the climate scenario used.


The Impact of Sea Level Rise

Global sea level rise is accelerating. Seas are now rising by 5mm per year, which is already impacting numerous cities around the world.

Due to increased coastal flooding and erosion, up to 1.5 million UK homes may be threatened by 2080. New government policies are urgently needed to protect homes, with the chief executive of the Committee on Climate Change saying that the current approach “really isn’t fit for purpose”, with the risk of up to £212 billion in annual coastal flooding damages by 2100.

Thames Barrier

Due in part to high tides, which had not been seen in the region for over 60 years, the UK Thames Barrier was forced to close 50 times during 2013–2014, as the Barrier having a design limit of a maximum of 50 closures during each year. A total of 1.25 million people live in the Thames Tidal Basin floodplain area; these are vhighly vulnerable to the devastating impacts of flooding if the Thames Barrier were to fail or be overtaken by greater-than-expected sea-level rise.

Risk of flooding

Coastal areas are facing significant risk from flooding, in part due to rising sea levels. Many communities are not taking coastal protection for granted, even where extreme storm surge is increasingly higher than the last event, and despite many smaller areas lacking criteria for government funding for flooding defense.