Long term weather patterns have been altered because of climate change, and more frequently include extreme weather events (see table below for some examples of altered weather patterns). According to a study published in Nature in 2015, climate change can be held responsible for three out of four temperature extremes, and almost 1/5 of heavy precipitation events globally. The study also states that on average the globe will experience 60% more extreme weather events. Heavy rains will be longer in duration, as more water evaporates due to the increase in global temperatures.
|Change in weather patters due to climate change. "Climate change 101 fact sheet"|
Wetlands help mitigate these extreme weather events in a few different ways, including controlling flood waters, purifying polluted water, and moderating drought. In this edition of Wetlands against Climate Change, we are going to look at how wetlands can “hold back the gates” and help mitigate flooding.
Wetlands are often compared to a sponge, because of their water-absorbing and holding abilities. For example peatlands have thick peaty soils, intricate mats of sphagnum moss and the roots of the peatland vegetation layer, that are able to absorb rainfall and snow-melt at amazing rates. According to a study done by Hallock et al in 2015 a 1 acre wetland that is 30 cm can hold 1.2 million liters of water. Once fully saturated, wetlands reduce the speed and volume of the water that enters the watershed. The water is forced to slowly percolate through the peaty soils and web of moss and roots. This allows water levels downstream to rise and fall slowly, so the whole system can adjust to the influx of excess water. Even relatively small wetlands can help protect large watersheds. According to a study done by Godschalk et al in 1999 a 2.3 hectare wetland can retain the natural runoff from a 166 hectare watershed!
|Squeezing water from sphagnum moss. (Photo by David Palmer)|
Wetlands do an incredible job of holding floodwaters, and they do it for free! This is just one of the many ecosystem services that wetlands provide. Researchers at the University of Waterloo, using computer simulations, found that leaving wetlands intact can reduce the financial costs of flooding by up to 29% in rural settings and up to 38% in urban settings. For example, at the urban study site, the average cost of flood damages if wetlands are maintained in their natural state would be $84.5 million, compared to $135 million if the wetland is replaced with agricultural development, resulting in a 38% cost increase. In the same study, if the wetland is replaced with urban development consisting of largely impermeable surfaces such as buildings, roads, sidewalks and parking lots, the cost savings of keeping the wetland intact is even higher.
|Natural urban wetland in Newfoundland. (Photo by Emma Bocking, DUC)|
If you add the other free ecosystem services provided by wetlands, including habitat protection, increased biodiversity, water purification, drought mitigation and carbon sequestration, it seems like a no brainer… wetlands save money and are an important part of Canadians self-identity.
Unfortunately, wetlands around the world have been part of a vanishing act. It is estimated that in the last 100 years 64% of the world’s wetlands have been destroyed through agriculture, dams, infrastructure and an increase in pollution. In agricultural practices, wetlands are ditched and drained in order to support crop growth. Draining has a negative impact on a wetland’s ability to mitigate flooding, and can lead to an 350% water flow increase during large flood events. As a result of wetland loss, floods caused by extreme weather events are more likely to cause damage in the form of soil erosion, property damage, loss of wildlife habitat, and loss of human life.
|Jesso family home, Benoits cove, NL January 2018 (Photo by CBC NL)|
1) Report activities in conservation areas that can harm wetlands like ditching or draining
2) Advocate for careful town planning that keep natural wetlands intact
3) Plant local and native plant species in your gardens and in your community
4) Avoid damaging wetlands on private property by keeping them an intact part of the larger system
5) Spread the word through outreach and education that wetlands are important to your community!
Flood mitigation is just one way in which wetlands can help during extreme weather events. Join us for our next blog “Keeping it Clean: Wetlands purifying water”!
CBC News “Don’t Drain the Swamp: Reports says wetlands help avert flood damage” Website. http://www.cbc.ca/news/politics/floods-wetlands-university-waterloo-feltmate-intact-climate-change-insurance-1.4199358
Ducks Unlimited Canada. “Wetland and Flood mitigation in Ontario: Natural Adaptions to climate Change” PDF/PowerPoint https://adaptationcanada2016.ca/wp-content/uploads/2016/04/Th3A-Steele.pdf
Environment Canada. 2009. “How Canadians Value Nature: A strategic and conceptual review of literature and research” http://www.biodivcanada.ca/default.asp?lang=En&n=900A6FFF-1
EPA “Why are Wetlands Important?” Website. https://www.epa.gov/wetlands/why-are-wetlands-important
Ficher, E. M., R. Knutti. “Anthropogenic Contribution to global occurrence of heavy-precipitation and high-temperature extremes” https://www.nature.com/articles/nclimate2617 Nature Climate Change, 5, 560 – 564 (2015).
Godschalk, D. R., Beatley, T., Berke, P. R., Brower, D. J., and Kaiser, E. J. (1999). Natural hazard mitigation: Recasting disaster policy and planning, Island Press, Washington, D.C.
Human Nature “5 things you should know about wetlands” Website. https://blog.conservation.org/2018/02/5-things-you-should-know-about-wetlands/?gclid=Cj0KCQiAuP7UBRDiARIsAFpxiRJpRtmrd9oORvff_ac-bItm9uWkO5hz128EYtYSrYcxFenOqEZFWOEaAnlWEALw_wcB
Huber, Daniel G. , Jay Gulledge. “Extreme Weather & Climate Change: Understanding the Link and Managing the Risk” Center for Climate and Energy Solutions: December 2011. PDF https://www.c2es.org/site/assets/uploads/2011/12/white-paper-extreme-weather-climate-change-understanding-link-managing-risk.pdf
Pomeroy, K. Shook “Improving and Testing Prarie Hydrological Model at Smith Creek Research Basin” PDF. http://www.usask.ca/hydrology/papers/Pomeroy_et_al_2014.pdf
Ramsar Fact Sheet #1 “Wetland Ecosystem Services: Flood control” PDF. https://www.ramsar.org/sites/default/files/documents/library/services_01_e.pdf
The Guardian “Extreme weather already on increase due to climate change, study finds” Website. https://www.theguardian.com/environment/2015/apr/27/extreme-weather-already-on-increase-due-to-climate-change-study-finds
Water Canada. “Wetlands important for mitigating flood impacts” Website. https://www.watercanada.net/study-wetlands-important-for-mitigation-of-flooding-impacts/
Watershed Council Tip of the Mitt. “Climate Change” Website. https://www.watershedcouncil.org/climate-change.html
“When the Big storm Hits” University of Waterloo. PDF. http://www.intactcentreclimateadaptation.ca/wp-content/uploads/2017/07/When-the-Big-Storms-Hit.pdf
Photos & Images:
Climate Change 101 Factsheet “Improve your project’s success: Consider Climate Change” PDF http://ecoadapt.org/data/documents/Climate101FactSheet.pdf www.freshwaterfuture.org and www.ecoadapter.org
CBC NL “Residents reeling from ‘unprecedented’ flooding on Newfoundland’s west coast” http://www.cbc.ca/news/canada/newfoundland-labrador/safety-priority-unprecedented-flooding-newfoundland-west-coast-1.4486657 (Jesso family home, Benoits Cove)
Squeezing water from Sphagnum moss © David Palmar www.photoscot.co.uk https://www.plantlife.org.uk/scotland/blog/our-flanders-moss-event-the-other-day-was-one-full-of-fun-and-information