Building and Restoring a Healthy Aquatic Ecosystem
Professor of College of Architecture and Landscape, Peking University;
Member of the American Academy of Arts and Sciences
Published in August 2021
In addition to the COVID-19 virus variants that keep threatening people all over the world, raging floods made headlines across the globe in July. From July 12 to the end of the month, floods in most affluent European countries, such as Germany, Belgium, and the Netherlands, killed 228 lives—Germany, “the hometown of engineers,” suffered from the worst natural disaster in the country since the North Sea Flood of 1962, causing 184 deaths. On July 20, 292 people died (by noon on August 2) in a cruel storm in Zhengzhou, China. These floods mostly took place in developed countries or regions—Maybe this implies the relation between natural disasters and human civilization. In the disaster-stricken cities, symbols of civilization—transportation systems, communication systems, as well as water-power systems—all paralyzed overnight. While many urban parks were little damaged and no severe floods were seen in the rivers inside the parks, the city’s daily service facilities have to faced huge risks. For instance, Zhengzhou Fuwai Hospital is located in the lowest part of the city.
Wide debates on the urban infrastructure construction arose since the 7·20 Zhengzhou Storm. In the eyes of the author, the most sticking problem is that modern cities often lack resilience to the uncertainty of natural disasters. In other words, on the whole, our aquatic ecosystems are sick. For cities with greater resilience, such storms would not lead to so much loss. However, it is the indestructible gray infrastructures—including the complex engineering facilities such as dams and large reservoirs—built with concrete and steel that turn these natural processes into “disasters.” In fact, besides floods, water disasters are increasingly frequent along with industrialization, urbanization, and global climate change, exacerbating the conflicts between human and water around the world, especially in China. The safety and health of the water and aquatic ecosystems has profound impacts on the sustainability of mankind and our living environment!
Water is essential to all ecosystems on the earth. The study of water health is difficult in isolation from Earth Sciences and Geography, but it still requires special attention. We exploring the distribution, mobility, and management of water, Hydrology emerged; We discovering the affecting patterns of water on organisms and the causality on aquatic ecosystem, Ecohydrology was proposed; We studying the coupled human-water system, Sociohydrology came into being. Later, disciplines that study water are viewed as Water Science. However, research in these disciplines still have not explored the water as a holistic system oriented subject, which is not only in the geographic and hydrologic sense, but also about the essence of life; which exists across spatial scales: habitats and sites, cities and regions, countries and the globe. Water interacts with land, cities, villages, animals, plants, humans and their activities, as the aquatic ecosystem, which covers not only the relationship of spatial patterns and processes between water and other landscape elements or water ecosystem and other ecosystems, but also the structures and functions within the ecosystem, including the interactions between the flows of materials, species, energy, and information. Human is indispensable, or even crucial to aquatic ecosystems at all scales.
Therefore, we need to evaluate, protect, and restore aquatic ecosystems/water systems based on the understanding of ecosystem services. The aquatic ecosystems provide supporting services, i.e. providing habitats, and supporting species spread, reproduction, and migration; provision services, i.e. providing water and aquatic products; regulating services, i.e. maintaining ecological resilience in response to environmental changes such as floods and droughts; and cultural services, i.e. fostering aesthetic tastes, cultural identity, sense of belonging, and offering recreational spaces. Unhealthy aquatic ecosystem cannot provide sound ecosystem services for humans, or worse, endanger human health or survival.
Maintaining the natural flow is critical to the health of aquatic ecosystem. In history, most damaging floods were caused by dyke bursting. Examples include the North Sea Flood in Germany in 1962 and the heavy flood in Zhumadian, China on August 8, 1975. The latter was one of the most disastrous in history, leading to tens of thousands of deaths, and also caused by serial bursting of the Banqiao Reservoir, the Shimantan Reservoir, and others. Recorded floods that took place along the Yellow River and caused huge loss of life and property also resulted from dyke bursting. The Vyion Dam in Italy built in 1960 was seen as the solidest and highest dam in the world of the time. On the evening of October 9, 1963, a sudden landslide shattered the entire reservoir, and nearly two thousand people died overnight—As the saying goes, “the harder the oppression, the more violent the resistance will be.” This is also true to the relationship between man and water. To harmonize with water, it is necessary to allow sufficient space for the natural flow. Although human beings are gaining greater freedom through the control over nature, but are more terribly retaliated by the nature at the same time. I’m not denying the achievements in human history, but pointing out that gray artificial techniques and facilities which go against nature would exacerbate the destructive force of nature due to the inadequate resilience.
Then, how large the space do we need for the natural flow of water? Take China as an example. In 2006, the research team from Peking University explored the security pattern of water conservation at the national scale, and found that as long as protecting and restoring the mountains, accounting for 43.6% of the total territory, the water conservation at the national scale will be greatly improved. This goal is possible for China, a country where mountains and hills account for nearly 70% of its territory. An analysis of the security pattern of flood regulation and storage showed that, under the monsoon climate, the annually flooded area ranges from 0.8% to 2.2% of the territory. Therefore, a romantic hypothesis would be that, after experiencing the unprecedented urbanization in history, the flood-prone land areas would be reserved for the natural flow. Then the human-water conflicts that have troubled China for thousands of years will be addressed radically.
However, this flood storage area, accounting for 0.8% to 2.2% of China’s territory, is the most fertile land on the floodplain (taking up a proportion of 6% to 15% of the arable land). It was unrealistic to turn arable land into flood storage area decades ago, when agriculture product contributed to most households’ income. But today it is no longer a fantasy: Agriculture product now accounts for only 8% of China’s GDP, and a considerable amount of arable land is left uncultivated in rural areas. Being impoverished due to excessive reclamation, the farmlands of floodplains and the whole farmland ecosystem could be restored by occasional inundation. Compared with the enormous investment in gray infrastructure projects for flood control, water system restoration is much more economical. More importantly, the damaged territorial aquatic ecosystem would be restored step by step as the increase of water space. The tens of millions of residents from the inundated areas can be well resettled through smart urbanization at the macro level, ecology-prioritized site selection and planning strategies for new towns at the medium level, and flood risk control measures such as building high platform at the micro level, together with the ecological wisdom of co-living with water and the building of a sound flood security system. However, large-scale hydraulic projects like barrages, levees and reservoirs, long-distance water diversion infrastructures across watersheds, waters invasions, and construction activities in low-lying areas, are endangering aquatic ecosystems.
A healthy aquatic ecosystem in cities, towns, or villages requires sufficient spaces for flood retention and storage in the built-up areas. Natural water storage, purification, and infiltration, as well as recharging of groundwater, ensures water circulation and stable water supply for wetlands and streams to nourish aquatic species. As water shortage is critical to China and other countries across the world, it necessitates the construction of resilient water ecological infrastructures to adapt to extreme rainstorms like “sponges,” thus guarantee the health of urban and rural aquatic ecosystems—This is also the goal of Sponge City construction. Many ancient civilizations left behind vast legacies in smart water management, such as developing terrace fields to conserve water, building ponds to regulate droughts and floods, creating mulberry-fish ponds in floodplains and deltas to foster local aquiculture, piling up soil on marshes to build water gardens, and digging ponds and ditches in urban and rural settlements. The history of the water-city co-existence in the Yellow River Basin tells that creating sufficient “sponges” (such as ponds and wetlands), as important water ecological infrastructures, can ensure urban resilience. The centralized drainage systems built with gray pipelines and deep tunnels made of concrete and steel are introduced to control urban flooding. But they often prove to be ineffective and unsustainable in urban water system management. Over-dependence on such infrastructures will put people’s lives and property at huge risks due to the global climate changes and uncertainties.
At the micro-scale of hydrophytic habitats such as water bodies and wetlands, a healthy aquatic ecosystem sees dynamic interactions between organisms and water. Organisms and water are interdependent. The absorption and transpiration of plants facilitate water circulation. The growth and decay of plants clean and enrich the nutrients in the water body. Species can multiply and migrate via water. To build a healthy aquatic ecosystem, we need to pay attention to the communities in wetlands, forms of waterfronts, courses of streams, and changes in beaches.
There are three strategies on how to build safe and healthy aquatic ecosystems: 1) Ensure the security pattern of water conservation and flood regulation, allow for water’s natural flow, and define the interface between human and water through water security pattern planning to rebuild human–water harmony; 2) Enhance the resilience of aquatic ecosystems by building “Sponge Land” —including Sponge City and Sponge Countryside, increasing on-site flood storage, slowing down water flow processes, and improving the resilience of tail-end sponges; and 3) Restore aquatic and hydrophytic habitats, promote deindustrialization, minimize the use of synthetic chemicals, rebuild the harmony between water and fields, human and the nature, and enhance the integration of blue–green spaces.
These strategies are all nature-based solutions. Instead of calling for reintroducing of the lifestyles or production modes of the agricultural age or the fishing-hunting age, the author encourages building a new ecological civilization upon legacies. Only in this way could we have healthy and beautiful water systems and territorial ecosystems, for a greater societal prosperity.
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Yu, K. (2021). Building and Restoring a Healthy Aquatic Ecosystem. Landscape Architecture Frontiers, 9(4), 4-9. https://doi.org/10.15302/J-LAF-1-010018
翻译 丨 田乐、肖杰
制作 丨 冉玲于