Fairlie Kirkpatrick Baird from NatureScot discusses their latest research that reveals the increasing risk of extreme drought in Scotland and how that may affect key habitats and their species.
One of the first things that comes to mind when people think of Scotland, alongside the beautiful mountains and the Loch Ness Monster, is the terrible weather. Scotland is famously wet, and as Highlanders we agree that you shouldn’t visit without a raincoat.
However, this soggy climate is changing, and it might surprise many people to know that Scotland suffers from drought, too. In fact, it’s getting worse.
Climate impacts
As climate change affects weather patterns, it’s well known that in Scotland, this will increase flooding and storms. However, our work suggests that there will likely be an increase in droughts here as well.
By using a combination of historic drought data and the UK climate projections, we produced a model showing drastic increases in drought in Scotland by 2040. These aren’t minor dry periods – our model looked at extreme drought, when water deficits fall below a certain threshold.
For context, the big UK drought in 2018 only just met this threshold in the drought index we used.
Findings
Some of these increases were quite alarming.
Whereas in the past, any given area in Scotland would experience extreme drought about one year in 20, our model suggests that by 2040 the same areas might experience extreme drought about one year in three. This increases to every 1.7 years in some of the most affected areas. The droughts are also likely to last longer – potentially up to 2-3 months more than in the past.
Interestingly, when we looked at seasonal differences, we found autumn was likely to be the driest. This might seem counterintuitive but is probably due to a build-up of water deficits over spring and summer, leaving low water tables in autumn. This could happen despite rainfall – surprisingly, an area can be in drought even after a storm if the water table was low enough.
Implications
Scotland has many iconic habitats and species that are well adapted to its typically wet conditions. Many of these are likely to be affected by drier conditions, particularly if droughts occur more frequently and last longer than they did in the past.
Rainwater-fed wetlands are a good example. These wetlands get most of their water from precipitation, whether rain, snow or sleet. In some ways, these habitats are quite resilient to drought, as some key plant species like Sphagnum mosses are often able to recover well from desiccation. However, if they dry regularly and for long periods, the impact is more severe and there’s less time to recover between droughts. Over time, this can change the species composition and lead to permanent damage.
Drought damage to wetlands can have a variety of knock-on effects, including changes in water and soil chemistry, and higher likelihoods of fire and erosion. Worryingly, drought-damaged peat wetlands will release more of the carbon trapped in their soil into the air, contributing to climate change.
As many of these wetlands are located in ‘hotspot’ drought areas, where increases are projected to be worst, this is a major concern.
Even though the rainforest is in the area of Scotland projected to experience least change in drought, many of its specialised species are very sensitive to even small increases. Similarly to wetland species, some are able to tolerate drying, but not for long periods or repeatedly over a short space of time. They are also vulnerable to competition, as they live alongside more drought-tolerant species that can easily overrun them during dry periods.
As some of these species aren’t found anywhere else in Scotland, or even in Europe, drought is a serious threat to their survival.
Recommendations
Drought is only recently being actively considered in climate change adaptation and mitigation planning in Scotland, and many strategies still focus on flooding and storms. We hope our drought maps, which highlight the hotspot areas of drought increase, will help managers to better assess the risks in their area and take it seriously as a threat in the future.
Read the full article: “Projected increases in extreme drought frequency and duration by 2040 affect specialist habitats and species in Scotland” in Issue 4:3 of Ecological Solutions and Evidence.
