Low-lying deltas are home to half the world’s population and much of its wealth, but they are also on the frontlines of climate change. Olivia Boyd looks at the challenges.
This year, officials in Jakarta realised they had a serious problem: rain – and more rain. Indonesia’s wet months are famously soggy and rainstorms nothing new for the capital. But this time around the downpours continued long after they were meant to have passed. “We have noticed there is no more dry season,” said Fauzi Bowo, the governor of Jakarta. “We use the dry season to repair and prepare our infrastructure for the rainy season. Now we have no chance. It rains every day.”
Jakarta, at the mouth of the Ciliwung River, is just one of many major global cities situated in low-lying, coastal deltas and already grappling with the effects of climate change. Deltas are areas of land formed from sediment where a river flows into the sea or another body of water. They are home to more than half the world’s population and many of its most valuable assets. The Nile Delta, for instance, accounts for more than 50% of Egypt’s economic activity through agriculture, industry and fisheries. But while proximity to water – and therefore global connections – has brought immense prosperity to many low-lying coasts, it also carries great risks, such as heavy rainfall, flooding and saltwater intrusion. These risks are now growing.
It was in this context that Bowo, speaking at an international conference on the impacts of climate change on deltas earlier this year, made his remarks. The gathering in the Dutch port city of Rotterdam brought together scientists and policymakers from delta regions across the world, from Vietnam to northern Italy, to share knowledge and ideas on adaptation and mitigation. It also acted as a launch pad for the Delta Alliance, a new network of cities and provinces working towards solutions to their common climate-related problems.
And the problems are significant. In 2001, the Intergovernmental Panel on Climate Change (IPCC) singled out deltas as some of the most vulnerable systems in the world. As Martin Parry, climate scientist at London’s Imperial College and former co-chair of IPCC working group II, said in Rotterdam: “Deltas already have high vulnerability – high flood risk, weather extremes. With climate change, these get worse.” Many deltas lie in the path of tropical cyclones, for example, and these are expected to increase in intensity as oceans warm. Their impacts can be devastating: in the week of the Dutch conference, a typhoon claimed the lives of 33 people in the Chinese province of Guangdong, in the Pearl River delta.
Precipitation patterns are just one of a host of concerns. Rising sea-levels in many places will compound existing flood risks and threaten freshwater supplies, as saltwater migrates upstream into rivers, and salinisation of coastal groundwater continues. Coastal floods will also threaten vital infrastructure, stressed Gerald Galloway, professor of civil and environmental engineering at the University of Maryland, in the United States: corrosion of pipes and flooding of water-treatment facilities and desalination plants, which need to be located near to the sea, could restrict the ability of societies to provide essential water services to their populations.
Another pressing issue for deltas is subsidence. Many deltas are, literally, sinking – a University of Colorado study published last year put the figure as high as 24 out of the world’s major 33. According to Robert Nicholls, professor of coastal engineering at the United Kingdom’s University of Southampton, in the twentieth century alone, Tokyo has gone down by as much as five metres in the worst affected parts, Shanghai by three metres and Bangkok by two metres. The downward motion heightens vulnerability to flooding, particularly when combined with sea-level rise.
Compaction of sediment over time means deltas have a natural tendency to sink but, said Nicholls, this process has been given a strong helping hand by humans. Withdrawal of groundwater and gas has accelerated compaction, while construction of dams restricts the flow of sediment that would otherwise reach the river mouth and build up the delta land. “Human activity is greatly increasing delta subsidence,” said Nicholls. “This reinforces the need to understand subsidence at the delta scale and mitigate human influences.”
A number of collaborative initiatives are trying to do just that. The United States Geological Survey (USGS), for instance, is working to help the Mekong Delta avoid the mistakes made by America in its management of the Mississippi Delta, where heavy damming and resource extraction have aggravated coastal degradation. Louisiana’s wetlands – which offer vital shelter against storms coming in from the Atlantic – are now disappearing into the sea at a rate of around one football pitch every 30 minutes. And, with them, a protective buffer is going too: research has indicated that storm surge is reduced by one foot for every 2.5 square kilometers of marsh, though the figures are debated.
Scott Wilson is chief of the spatial analysis branch at the USGS National Wetlands Research Center. He said: “Hydroelectric dams are huge in terms of discussion on the Mekong River and we in the States have done the same thing – we’ve committed dams, mainly for navigation concerns rather than hydroelectric, which have had a huge impact on our coastal system. That coastal system provides not only communities for people to live in, but also recreation opportunities and fisheries. All of that has been impacted by these dams. The Mekong is where the Mississippi was 80 years ago. They’re at that point where they’re going to make some critical decisions. And hopefully we can help them to make informed decisions.”
This partnership is just one of countless initiatives intended to share best practice between deltas and coastal cities. Larger organisations include Connecting Delta Cities, a Dutch-led network of cities active in climate-change related development and adaptation; C40 Cities – a group of major cities “committed to tackling climate change”, a large proportion of which are coastal. And, of course, the freshly launched Delta Alliance, which in its first phase is connecting four hubs – California, the Netherlands, Indonesia and Vietnam – but is already in the process of expanding to include countries such as China and Egypt.
Looking to others will not, of course, solve every problem. The range of challenges is wide and each delta will be affected differently. As Princeton University geoscientist Michael Oppenheimer explained in a keynote address in Rotterdam, even sea-level rise – often communicated to the public using a bathtub analogy, with water distributing evenly – will not in fact be uniform. Some areas, such as the east coast of the United States may see higher than average rises; some places may even see falls. And uncertainty about precise impacts remains paramount. But, stressed Oppenheimer, this is not a reason for inaction: “The uncertainties are very large and unlikely to shrink soon. We shouldn’t wait for scientists’ knowledge to get us out of these problems.”
A man in a position to agree with this is Cedric Grant, deputy mayor of New Orleans, which in August marked the fifth anniversary of Hurricane Katrina, the devastating storm that flooded 80% of the city and killed more than 1,800 people. “Short term solutions are half measures, that will no longer suffice,” he said. “Storms are more powerful and more destructive and our coast has been degraded so severely that it can no longer protect New Orleans. These are some of the world’s most complicated challenges and some of the most costly to address. But we have no choice but to face them head on.”
Olivia Boyd is assistant editor at chinadialogue.
Homepage image by /ah Lun