Are sinkholes connected to the climate crisis?

The climate crisis is increasing the frequency and severity of extreme weather around the world, leaving some regions exploding in wildfires and others deluged by floods.

Such events can feed into a cascade of problems - including on the land under our feet. Scientists now recognise that the climate crisis is having an impact on more frequent and intense natural geohazards like landslides, debris flows and earthquakes. And then there’s the sinkholes.

This week three large sinkholes appeared in The Villages in Florida, draining water from ponds and shutting down a nearby recreation centre and swimming pool. Another caused road closures in Allen County, Indiana while an eight-foot deep sinkhole opened in New York.

Over the last month sink holes have opened up across the UK in Bolton, Doncaster, Kent, Gloucestershire, Bracknell and Devon, causing road closures, damage to property and structural concerns.

According to the British Geological Survey, sinkholes can appear following heavy rain or surface flooding. They can result from leaking drain pipes or burst water mains during building work. Changes in the water table level and even mining can cause a sinkhole to open.

There are two basic types: those created slowly over time (called a cover-subsidence sinkhole) and those that appear suddenly (a cover-collapse sinkhole).

Sinkholes typically collapse into a void which has opened up in the Earth through a natural process. However in urban areas they can also open up existing human-made holes.

The sudden, dangerous voids have been linked with heavy construction work and the extraction of water from the water table.

But research has also directly linked the increase in sinkholes to the climate crisis.

Using Florida as a case study, researchers have recorded strong correlations between high temperatures and the formation of sinkholes.

The state has had among the highest number of sinkholes in the world - more than 2,800 since 1950.

According to research in the European Geosciences Union journal, Natural Hazards and Earth System Science, there is a clear correlation between sinkhole collapse and peak drought periods.

“Three distinct drought and sinkhole collapse phases are evident between 1965 and 2006, along with eight peak periods of sinkhole collapse that lag slightly behind eight peak drought periods,” the authors wrote.

“The results of this study confirm that global warming related to climate change has led to an increase in sinkhole collapse events in Florida over the past 50 years.”

The study found that for every 0.1C rise in global temperature, the number of sinkholes increased between 1 and 3 per cent.

Increases in extreme weather are likely to exacerbate the problem.

Dr Vanessa Banks of the British Geological Survey told The Independent: “In Florida the sinkholes form around the water table and propagate up. If that water table fluctuates, which it would do when you have changing amounts of rainfall, then yes there is a propensity for that to be impacted by climate change.

“If the direction in Florida is towards increased rainfall or increased storminess and higher intensity rainfall, these events lead to local rises in the water table [exacerbating the problem].

“A sinkhole can be defined as a naturally occurring feature, or it can be thought of, in an engineering context, as a ‘collapse subsidence feature’.”

Dr Banks said both naturally occurring voids and those “capped” voids covering human-made holes “can be influenced by changes to the climate”.

“During 2016, we had a flurry of sinkholes in London and that was because the weather system at the time was pushed south by the jet stream – it led to the flooding of the Somerset Levels – and there was also an increased number of landslides. So the BGS was reporting to the government’s Science Advisory Group for Cobra on the numbers of events as they took place,” she added.

“We noticed a significant increase in landslides and sinkholes, and of those sinkholes, around 50 per cent were related to anthropogenic activity, and 50 per cent were naturally occurring.”

“The influence of dry weather can also be very important,” she said, as cracks form in soils which subsequently struggle to bind as firmly as before.

They can become wedged open with different substrates and even form new pathways for water, leading to opportunities for subsidence and eventual collapses.