In this latest blog we hear from DCRT Project Assistant, Beckie Fulton, on Climate Change and the impact on our rivers.
What is Climate Change?
Climate change is a hot topic in the news this week as more than 190 world leaders gather in Glasgow, Scotland for the UN Climate Change Conference (COP26). The summit aims to bring together world leaders, negotiators, government representatives, businesses and citizens to discuss what actions can be taken to accelerate towards the goals of the Paris Agreement and the UN Framework Convention on Climate Change⁽¹⁾.
Climate change is the long-term shift in weather patterns and global temperatures. Geological records show that these shifts can occur naturally. However, since the 1800s, human activities such as burning fossil fuels like coal, gas and oil, has exponentially increased greenhouse gas emissions and is the main driver of modern-day climate change⁽²⁾. Greenhouse gases include Carbon Dioxide, Methane, Nitrous Oxide, Water Vapour and Fluorinated Gases (which are synthetic). These greenhouse gases act like a blanket wrapped around the Earth and trap in all the heat which normally escapes back into space. Over time this leads to an increase in global temperatures, since the late 1800’s greenhouse gases have already resulted in the Earth warming by around 1.1°C⁽²⁾.
The latest figures show that on average we are emitting around 51 billion tons of greenhouses gases in a year⁽³⁾. In order to reduce the impacts of climate change (which we are already beginning to see) we need to reach net-zero greenhouse gas emissions by 2050, and half our emissions by 2030. This was agreed by international science committees as it would limit global temperature rise to no more than 1.5°C, which will help us to avoid the worst impacts of climate change and maintain a liveable climate⁽²⁾. Reaching these targets will be incredibly hard. During the COVID-19 Pandemic, when the world and economy came to a halt and millions lost their lives, greenhouse gas emissions only reduced by around 5%, which means we emitted 48-49 billion tons instead of 51 billion tons⁽³⁾. Thinking about this makes it hard to imagine how we will ever manage to reach our net-zero emissions goal by 2050. But we must achieve this, or we will see devastating changes to our natural world before the end of the century.
How will climate change impact our rivers?
Now we have discussed what climate change is and the seriousness of the situation, let’s talk about how climate change will impact our rivers. The main ways climate change will impact our rivers are: flooding, drought, water quality and ecosystems.
Flooding and Drought
Flooding and drought are often what people first think about when asked how climate change will impact our rivers. As mentioned earlier climate change is the long-term shift in weather patterns and global temperatures. Firstly, rising temperatures increases both evaporation from land and water surfaces. As a result of shifting weather patterns, there can be prolonged periods of time with no/ minimal rainfall. The combination of these two factors results in severe and long droughts.
Also, warmer air can hold more water vapour and in addition to increasing rates of evaporation more extreme rainfall events are triggered – this means greater volumes of water falling at higher intensities.⁽⁴̛ ⁵⁾. Rainfall intensity depends on how much water vapour the air can hold; research suggests that the air can hold 7% more water vapour for every 1°C rise in temperature⁽⁶⁾. Rain that falls during these intense events does not have the chance to soak into soils but rushes straight off increasing surface runoff, particularly in compacted soils or soils damaged by drought. This means that the rainwater will reach the rivers faster, and as the rivers do not have the capacity to store all this sudden extra water, it causes a flood. As climate change continues to worsen, we will start to feel the impacts as flooding and drought events increase in both frequency and severity.
Another impact of climate change that we will see in our rivers is a change in water quality. This aspect links into the flooding and droughts that we will experience. When extreme rainfall occurs after a drought it will lead to an increase in soil erosion and will also transport any harmful chemicals, from pesticides or herbicides, that have accumulated on the top soil into our rivers⁽⁴⁾. It will also wash into the river toxic chemicals that build up on warm roads during dry weather ⁽⁵⁾. Washing toxic chemicals into our rivers can have a devastating impact on the plants and animals that live there. These chemicals could make the river uninhabitable for species of fish and plants, which in turn will decrease the biodiversity in our rivers. Not only will this harm our biodiversity, but these toxic chemicals can also be washed into our fresh water supplies that we use for drinking water.
Another way in which the water quality of our rivers will decrease is through sewage pollution. During intense rainfall excessive storm waters become a big problem for sewage disposal. The sudden increase in water levels cause overflows at the sewage treatment plants and the raw sewage enters our rivers through combined sewer overflows (CSOs)⁽⁵⁾. As with the toxic chemicals from run off, this sewage pollution will decrease water quality and have harmful effects on our wildlife. CSOs are already discharging outside of extreme weather conditions and changes are starting to happen to address this but with climate change increasing the frequency of high-intensity rainfalls and storms and CSO discharge as a result, much more needs to be done to prevent this form of pollution. More on this is available here.
Our rivers are freshwater ecosystems and climate change is impacting these systems not just by altering the temperatures but also by changing water flows regimes. Flow regimes are patterns in flow variability such as long-term monthly and annual means and high and low flows⁽⁷⁾. Research has shown that changes in these flow regimes (as a result of climate change) will have a large impact on our freshwater ecosystems⁽⁸̛ ⁹⁾. Such impacts include the lower water column depth on the spawning of salmon and impacts of reduced runoff on breeding grounds for water birds ⁽¹⁰⁾. Another impact to our rivers ecosystem in the UK is invasive species. Recent research indicated that climate change will raise river water temperatures and may promote higher Signal Crayfish performance in the future, which will further enhance the ecological impacts this invasive species is already having⁽¹¹⁾.
What can we do?
Although the climate change situation may seem bleak, it is not too late to make changes and limit the impacts we will start to see in the coming decades. There are two main ways we can do this: mitigation and adaptation. Mitigation involves actively tackling the issue of climate change by reducing greenhouse gas emissions, whereas adaptation involves developing measures to help limit the impacts of climate change.
The Rivers Trust is currently doing amazing work to help lower greenhouse gas emissions for everyone. There are 4 main ways Rivers Trust’s are doing this across the UK:
- Planting trees – As I’m sure many of you know trees take in carbon dioxide from the atmosphere, which helps reduce the amount on greenhouse gases, thus helping to reduce warming. Local Rivers Trusts planted 300,391 trees in 2020⁽¹²⁾.
- Saving Soil – Soil has the ability to store carbon. This ability is maximised when the soil is healthy. The Rivers Trust is working with landowners and famers to make their soil healthy to maximise their soils ability to hold carbon⁽¹²⁾.
- Water Quality – By cleaning up our rivers and removing pollution from the water we are reducing the amount of energy that is required to clean it before it enters our homes and businesses. 630 water quality improvements and pollution events were dealt with by The Rivers Trust in 2020⁽¹²⁾.
- Creating and Restoring Wetlands – 90% of wetland habitats have been lost in the UK in the last 100 years. Wetlands are important for biodiversity but also important for tackling climate change, as they can store huge amounts of carbon. As well as this they act as a natural filter to remove specific nutrients that can cause problems downstream such as algal blooms. Local Rivers Trusts created and restored a total of 62 wetlands in 2020⁽¹²⁾.
As mentioned previously the frequency and severity of events such as flooding will increase as a result of climate change. However, there are ways in which we can try to minimise the impact these events have on our local communities. There are 3 main ways The Rivers Trust is aiming to adapt to climate change
- Natural Flood Management (NFM) – As climate change worsens our floods, we cannot keep just building bigger and bigger flood defences. NFM is using natural processes to help reduce the impact of flooding by capturing and slowing the flow of water through the landscape before it reaches the main river network. This includes a whole range of measures including soil management, tree planting and wetland creation. Many of you have helped us install leaky dams too, another technique that is used in the upper catchment to slow the flow of flood waters into the main rivers. Holding this water back for a period of time will allow the main river to deal with the extra input of water better. Additionally, leaky dams can push water onto the surrounding flood plains and allow it the time it needs to infiltrate the soil, work through the ground and recharge underground aquifers that we use for drinking water, that run low during droughts. Scour pools created downstream of leaky dams can also become vital refuges for wildlife during the drier summer months. In 2020, 248 NFM schemes were put in place by local Rivers Trusts⁽¹²⁾.
- Improving Connectivity – Connectivity is important at it links habitats together and provides pathways for species to adapt to climate change by altering their distribution. This is why the Rivers Trusts mission to restore our rivers and their connectivity to different habitats is so important⁽¹²⁾.
- Cooling Cities – The Urban Heat Island (UHI) effect is becoming an increasing problem in the UK due to rising temperatures and more frequent heatwaves⁽¹³⁾. Evaporation from surface water in cities has the ability to create a cooling effect. Research conducted on the River Don, Sheffield showed a mean level of daytime cooling of over 1.5°C above the river in spring, the amount of cooling varied throughout the year, particularly in the summer when water temperatures were higher⁽¹³⁾. The type of urban development that was on the river banks impacted the amount of cooling felt away from the river. The Rivers Trust aims to make sure urban rivers, such as the River Don, are protected to continue this urban cooling effect⁽¹²⁾.
Rivers Trusts across the UK are working with nature to protect our river ecosystems from the impacts of climate change and environmental damage, but this serious worldwide problem requires a dramatic reduction in greenhouse gas emissions and the switch to clean, reliable energy sources before ecosystems are irreversibly damaged by global warming.
⁽¹⁾ United Nations. UN Climate Change Conference (https://www.un.org/en/un-climate-change-conference-cop-26). [Accessed 02/11/2021].
⁽²⁾ United Nations. What is Climate Change? (https://www.un.org/en/climatechange/what-is-climate-change). [Accessed 02/11/2021].
⁽³⁾ Gates, Bill. (2021) How to Avoid a Climate Disaster: The Solutions We Have and the Breakthroughs We Need.
⁽⁴⁾ Qui, J., Shen, Z., Leng, G. & Wei, G. (2021) Synergistic effect of drought and rainfall events of different patterns on watershed systems. Nature: Scientific Reports. 11:18957.
⁽⁵⁾ UK Rivers Network. Climate change and rivers: a brief introduction. (https://www.ukrivers.net/climate.html) [Accessed 03/11/2021].
⁽⁶⁾ Tyndall Centre for Climate Change Research. UK rain is going to get heavier. (https://tyndall.ac.uk/news/uk-rain-going-get-heavier/#:~:text=At%201.4%C2%B0C%2D4.6,resulting%20in%20more%20intensified%20rainfall.&text=Further%20intensified%20rainfall%20also%20increases%20risk%20of%20flooding) [Accessed 03/11/2021].
⁽⁷⁾ DÖll, P. & Zhang, J. (2010). Impact of climate change on freshwater ecosystems: a global-scale analysis of ecologically relevant river flow alterations. Hydrology and Earth System Sciences, 14, 783-799.
⁽⁸⁾ Poff, N. L. & Zimmerman, J. K. H. (2010) Ecological responses to altered flow regimes: a literature review to inform the science and management of environmental flows, Freshwater Biology, 55, 194– 205.
⁽⁹⁾ Matthews, W. J. & Marsh-Matthews, E. (2003) Effects of drought on fish across axes of space, time and ecological complexity, Freshwater Biology, 48, 1232–1253.
⁽¹⁰⁾ Kundzewicz, Z. W., Mata, L. J., Arnell, N. W., Doll, P., Kabat, P., Jimenez, B., Miller, K. A., Oki, T., Sen, Z., & Shiklomanov, I. ´ A. (2007). Freshwater resources and their management. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, edited by: Parry, M. L., Canziani, O. F., Palutikof, J. P., van der Linden, P. J., and Hanson, C. E., Cambridge University Press, Cambridge, UK, 173–210.
⁽¹¹⁾ Rodriguez Valido, C. A., Johnson, M. F., Dugdale, S. J., Cutts, V., Fell, H. G., Higgins, E. A., Tarr, S., Templey, C. M. & Algar, A. C. (2020). Thermal sensitivity of feeding and burrowing activity of an invasive crayfish in UK waters. Ecohydrology, 14(1), doi: 10.1002/eco.2258.
⁽¹²⁾ The Rivers Trust. Rivers can help us cope with the climate crisis. (https://www.theriverstrust.org/key-issues/climate-change). [Accessed 03/22/2021]
⁽¹³⁾ Hathway, E. A. & Sharples, S. (2012). The interaction of rivers and urban form in mitigating the Urban Heat Island effect: A UK case study. Building and Environment, 58, 14-22.