Impacts of climate change on archaeological preservation

 

Water table

In many wetland areas the decrease in summer rainfall combined with continued demand for water from vegetation cover could result in a drop in the water table leading to the eventual loss of some sites and any associated organic based archaeological materials. In contrast, the water table of low-lying wetlands subject to tidal influences may increase as a result of proposed sea level rise.

Flooding

Wet woodlands can be used to help stabilise land surfaces during flood events, but sea level rise could potentially cause flooding to become permanent or brackish in water quality, resulting in probable tree death. However, with sea level rise of 1m or less, the areas of woodland to be affected are likely to be small.

Vegetation cover

Extended periods of drought can result in the death of existing vegetation creating areas of bare earth with minimal plant cover. Rainfall events during the summer months are predicted to occur as heavy storms with the total winter rainfall likely to increase. Any loss of vegetation cover may therefore heighten the risks of archaeological loss through soil erosion, landslides and flash flooding.

Soil moisture

Trees will compete with other vegetation for available moisture to grow and in areas where soil moisture is critical for archaeological preservation, vegetation and drainage management may be necessary to reduce unwanted artefact desiccation.

Other soil changes

For many soils, a loss in carbon is predicted and this, in turn, will reduce the soil’s water holding capacity. Increased soil temperatures may also increase the rates of chemical reactions within the burial environment, for example changes in soil pH are predicted, although the direction of change will be site-specific.  All of these soil changes will, in turn, alter the types of soil organisms present.

Any combination of the above changes to the soil environment will have implications for the burial environment and may be beneficial or detrimental to archaeological preservation.

Above ground, the enhanced seasonal extremes of soil moisture content will increase the shrink-swell movement of susceptible clay soils, promoting the occurrence of building subsidence, potentially putting historic buildings and structures at risk on instability.

Windthrow

Heavy storms in conjunction with eroded soils may also increase the risks of windthrow, as the predicted higher winter rainfall results in more water-logged soils leading to root death and increased soil slippage.

Fires

Prolonged summer droughts will increase the risks of fires, potentially causing significant damage to any heritage features within their path.