Civil Engineering January-February 2022 | Vol 30 No 1

Civil Engineering January/February 2022 7 W etlands are globally important for sustainable develop- ment, acting as biodiversity hotspots and carbon sinks, and providing freshwater stores and numerous sources of livelihood. World Wetlands Day is celebrated each year on 2 February to raise awareness about wetlands and mark the anniversary of the Convention on Wetlands, which was adopted as an international treaty in 1971. When it comes to global warming, wetlands have a vital role to play. Peatlands and wet grasslands act as natural sponges, providing freshwater storage that can help safeguard against drought, while coastal wetlands reduce the speed and height of storm surges and protect against coastal erosion. Despite cov- ering just 3% of the world’s land area, peatlands alone hold 30% of all carbon stored on land – twice the amount stored in all the world’s forests. Unfortunately, scientific estimates indicate that 64% of the world’s wetlands have disappeared since 1900. The decline is hap- pening fast, with 35% losses since 1970. One of the consequences of this is that access to fresh water is declining for as many as two billion people worldwide, while flood control, carbon storage, and traditional wetland livelihoods suffer. According to the 2018 Global Wetland Outlook, water quality trends are mostly negative. Untreated wastewater, industrial waste and agricultural runoff have contributed to worsening water pollution in almost all rivers in Latin America, Africa and Asia. It is estimated that by 2050, one-third of the global popula- tion will be exposed to water containing excessive amounts of nitrogen and phosphorous, leading to rapid algal growth and decay that can kill fish and other species. SAVING OUR WETLANDS We can learn a great deal from nature to create sustainable water storage and purification systems. Wetlands act as natural filters, trapping sediment, nutrients, and even pathogenic bacteria. The chemical and biological processes that take place in wetlands can also help trap pollutants such as heavy metals and pesticides. Given its purification abilities, the need to protect ecological infrastructure, such as wetlands, is highlighted by the state of South Africa’s raw water quality. Between 1999 and 2011 river health deteriorated across all nine of South Africa’s water management areas. During the same time period, the extent of South Africa’s main rivers classified as being in a poor ecological condition increased by 500%, with many rivers pushed beyond the point of recovery, while tributaries in a poor ecological condition increased by 229%. South Africa’s National Water and Sanitation Master Plan (NW&SMP) estimates that the country has lost over 50% of its wetlands, with the remaining 3.2 million ha considered to be in a poor condition. This limits their ability to regulate water flow and purify water. Degraded ecological infrastructure loses its ability to release water in times of drought and recharge groundwater supplies, increases the vulnerability of people and built infrastructure to floods, and increases maintenance and repair costs on built infra- structure. In fact, the NW&SMP states that, “It is often more cost- effective to rehabilitate ecological infrastructure than to be faced with an ongoing need to repair or replace built infrastructure.” Unfortunately, the highly valuable role that ecological infra- structure can play is largely under-realised and undervalued in a society that prioritises built infrastructure solutions. Agriculture, mining and urbanisation are all placing severe pressure on ecological ecosystems, many of which are poorly protected, ultimately leading to their degradation and loss. It is vital that the maintenance of ecological infrastructure is incorporated into the planning and construction of built infra- structure. Just like built infrastructure, ecological infrastructure needs to be maintained and restored in order to deliver important socio-economic benefits. REFERENCES www.ramsar.org . www.worldwetlandsday.org . Global Wetland Outlook: State of the world’s wetlands and their services to people. 2018. Available: https://www.ramsar.org/sites/default/ files/documents/library/gwo_e.pdf . National Water and Sanitation Master Plan, Volume 1: Call to Action, Version 10.1. Available: https:// www.gov.za/sites/default/files/gcis_ document/201911/national-water-and- sanitation-master-plandf.pdf . Danielle Petterson Editor: Civil Engineering danielle@saice.org.za Le t ter from the ed i tor Prioritising green infrastructure As global warming increases so too does the likelihood of longer and more frequent periods of drought for South Africa. Natural features like wetlands have an ever more important role to play but, unfortunately, they are declining at a rapid pace. “It is often more cost-effective to rehabilitate ecological infrastructure than to be faced with an ongoing need to repair or replace built infrastructure.”