资源环境科技发展态势分析平台

Earth has a water problem.

Water crises in Cape Town and Southern California have shined a light on the plight of the planet’s fresh water in the face of climate change — and the critical role that nature plays in addressing today’s most pressing water challenges.

A new paper published in the scientific journal Ecohydrology and Hydrobiology looks at the gravest threats to our water security — and explores how nature can help us protect and manage the global water supply, sustainably. It’s this focus on nature-based solutions that drives the study’s “21st century approach” to addressing the world’s water problems.

The paper makes the case that, while traditional engineering approaches have immediate benefits in addressing water problems, they can be costly to install and maintain, are often not designed well to respond to climate change and they impair the environment. These engineering and technology approaches are not enough to tackle water crises in the face of climate change, according to Ian Harrison, a freshwater specialist for Conservation International, and one of the paper’s co-authors. In a recent interview, Human Nature spoke with Harrison about the paper.

Q: What’s going on with the planet’s fresh water?

A: The World Economic Forum report for 2017 ranks freshwater supply at No. 3 on a list of the top 10 global risks in terms of impact on humanity. That’s surpassed only by weapons of mass destruction and extreme weather events.

Compounding these problems: climate change, which is affecting people now. Where I live in northern Arizona, last year we experienced the sixth driest fall and winter on record, and there is little indication that it is going to get better in the near future. The trees where I live are water stressed and less resistant to attack from pests like bark beetle, and so are more likely to die and provide fuel for fires. In addition, the drought in this area means that human water requirements are drawing down on already depleted supplies, so we are constantly making the problem worse. Even the mighty Colorado River is showing declining flows, and with increasing demands for freshwater, it could result in cutbacks in supply to Mexico, Arizona and Nevada.

Q: So, what does that mean for humans?

A: The simple answer: We’re using more water as the global population grows, and eventually we’re going to run out (in fact, in some places, we nearly have). For years, nations have tended to address the problem of water security by developing hard (or “gray”) infrastructure and technology (eg., dams and channels) that may deliver water to people, but they have had a serious impact on freshwater habitats and species, reducing the ecological integrity and the capacity of these ecosystems to deliver other important benefits. So while solving the immediate problem of getting freshwater to people, they’re creating more problems for the future.

Countries are looking at how to address this issue in the context of the Sustainable Development Goals (SDGs), a set of 17 overarching goals ranging from creating sustainable cities and ending hunger to conserving life on land and water. Our paper looks at the role of nature in achieving these goals. What we’ve seen is that as nations seek to develop sustainably and to limit the impacts of climate change, a critical part of that will be the sustainable use of freshwater ecosystems, avoiding actions such as draining peatlands, or flooding forests via dam construction, that can increase the production of greenhouse gases. These are the specific ways in which our concepts can be applied at the national level.

We cannot keep thinking and working along these standard lines of relying on engineering and technology for all the answers. Instead, we must look at how we can make better use of our natural ecosystems — our available “green” infrastructure, in comparison to the gray infrastructure.  What we need is a 21st century approach: One that addresses the challenges of today using our knowledge of the natural benefits provided by healthy ecosystems.

Q: Your paper recommends a “21st century approach” to addressing water problems. What does that look like?

A: The scientific community recognizes that the world’s freshwater ecosystems are in a dire state, with widespread habitat loss within and around wetlands, lakes, rivers, etc.; increased water abstraction (extraction of water from lakes, rivers, groundwater, e.g., for use in irrigation) and pollution; and increasing numbers of invasive species, which threaten native plants and wildlife.

To protect our remaining freshwater ecosystems, we need to consider them as a key component of development decision-making, not as an after-thought to it. These ecosystems (green infrastructure) naturally provide us with more than US$ 4 trillion of services annually, so their sustainable management represents an important investment for governments. Therefore, we must have a well-informed decision-making process that enables us to identify where to invest in maintaining our natural ecosystems, where we might have to rely on traditional gray infrastructure and where our most practical option is a blend of the two.

This is not simply an abstract concept — there are several very good examples where aquatic ecosystems have been conserved or restored in the Netherlands, the most densely populated country in Europe, to buffer against the effects of climate change.

Q: How do we actually implement these nature-based approaches?      

A: While the importance of freshwater ecosystems as suppliers of water for drinking, for irrigating crops and for generating electricity is (I hope) obvious, the freshwater ecosystems of the world provide many other benefits to us that may less visible: water purification, nutrient recycling, flood protection, even recreation. These are equally important for social and economic reasons, and they all require a well-functioning ecosystem that can maintain its natural ecological processes.

Our paper identifies some specific challenges to achieving this stronger focus on green infrastructure and explores how to maximize the benefits of nature-based solutions at the global scale. These challenges include:

• Insufficient and ineffective coverage of freshwater ecosystems by protected areas;
• Insufficient research on how to blend human-engineering with natural ecosystems;
• Insufficient monitoring networks on the extent and status of freshwater ecosystems and their functions;
• Insufficient technical capacity and knowledge to implement green-gray infrastructure management approaches, particularly in the developing world where these new approaches can have these greatest effect.

But we also identify a set of four globally significant actions that can help us address these challenges.

Q: Walk us through those.

A: First, there’s the creation of green infrastructure watershed “banks.” These are ecosystems whose natural assets represent a reserve of water resources and freshwater services for long-term, cost-effective human use. For example, the Chingaza-Sumapaz-Guerrero corridor region, a focal area for Conservation International, provides water to the city of Bogotá, Colombia. Freshwater protected areas represented important investments in this “bank,” because of their role in supplying water of adequate quality and quantity to downstream populations. 

Second, we advocate an accelerated global research and solutions program on coupled human-environment engineered systems, based on cost-benefit analyses. This will provide the backbone of scientific and socio-economic research necessary to evaluate how to integrate green infrastructure with existing gray infrastructure actions, to attain universal water security.

Third, we support new global water-ecosystem services observatory to assess progress (or lack of it) in sustainable management of water assets. This will fill the existing gaps in the global monitoring networks of freshwater ecosystems and their functions. It should combine state-of-the-art Earth observations with ecosystem monitoring on the ground and use simulation models to show real-time change in ecosystems, from the local to the global scale.

Finally, we encourage an expanded capacity/workforce development initiative. This will create universal readiness among U.N. member states to produce the next generation of environmental planners and water practitioners.

Q: Now that your research has been published, what’s the next step?

A: What’s clear is that our planning for conserving and managing freshwater ecosystems must not focus only on the services they provide to people. We also need to consider the needs of the species and the habitats that are the core of healthy ecosystems.

An important point to stress here is that although we are talking about big, global issues, the solutions are also based on what we, individually and as communities, do every day. Cape Town’s Zero Day, when the city was expected to run out of water, has not gone away. It has just been delayed from the initial expected date in March 2018 to sometime in 2019. This is a direct result of how the people and city managers of Cape Town have responded to the threats and successfully conserved their water in only a short period of time. That shows us that we can change our behavior and mitigate threats, but the message from Cape Town (and for me in Arizona) is that our decision-making should be proactive, not reactive.

We should be making these decisions about how we manage our freshwater and the ecosystems that supply it now, when we have the freedom to think adaptively, not later, when we will be forced to act in response to ever more frequent emergencies.

Ian Harrison is Conservation International’s freshwater specialist. Sophie Bertazzo is a senior editor at Conservation International.

Further reading

• Parched Cape Town’s lesson for cities: Protect nature
• New tool provides gauge for freshwater health
• To protect its precious water, Bogotá looks to the Big Apple