How a new planning approach can transform degraded waterways into centers of aquatic habitat restoration

Buried in the concrete of our cities lies one of the most pressing environmental challenges of our time. Often reduced to artificial canals or packed under layers of asphalt, urban waterways They actually hold the key to responding to a silent but devastating global crisis: the collapse of the freshwater ecosystems.

A recent international study overturns the classical perspective of urban planning: if until now cities have been the main drivers of this degradation, today scientific research demonstrates that urban fabrics themselves can become the thousand beating hearts of a global commitment to the restoration and recovery of freshwater ecosystems.

Freshwater crisis: an emergency that threatens our very existence

Rivers, lakes and wetlands occupy just over 2% of the Earth's surface, yet they are home to almost 10% of all animal species known and described. However, freshwater ecosystems are also among the most threatened: global wetland loss is proceeding at a rate three times higher than that of deforestation, and only 37% of the planet's longest rivers still flow freely along their entire length. Thus, in the space of a few decades, Freshwater vertebrate populations have declined by approximately 84%And urban waterways are at the center of this rapid decline.

As stated in a study recently published in the journal Journal of Environmental Planning and Management, the main threats to these ecosystems are the habitat loss and degradation, pollution, modification of hydrological flow, fragmentation, hydroclimatic changes, overexploitation and invasive aquatic species – danger factors that inevitably increase in the urban context:

“In urban environments, these persistent and emerging threats are intensified by concentrated land-use change, infrastructure expansion, and hydrological alteration.”

According to researchers, we are in the midst of a freshwater biodiversity crisis – a crisis that must also be addressed with informed urban planning. Although our cities are home to some of the world's most degraded rivers, wetlands, and ponds, the researchers explain, they also offer enormous opportunities to protect and restore freshwater wildlife.

Waterway Engineering: The Illusion of Water Control

Ancient civilizations, from the Indus to the Maya, built their settlements around water, working with floods, wetlands, and seasonal flows to support both people and nature. Then, the researchers explain,

“With the advent of industrialization and modern planning, floodplains were built, rivers were straightened, streams were buried, and increasingly designed to move water through cities rather than to support wildlife.”

Today's cities were designed with people in mind. In this Western and anthropocentric approach Planning has prioritized housing, transportation, and economic growth over integrating less cost-effective, short-term green design solutions.

A classic example of how this impacts freshwater biodiversity is given by the urban stormwater removal, a top priority for preventing flooding and property damage. However, the need for protection from water has led to a reliance on soil sealing, which in turn reduces groundwater recharge, facilitates flooding, and contributes to thermal pollution and increased nutrient and metal concentrations from surface runoff.

The result is that today many urban waterways are degraded, freshwater species continue to decline and entire cities find themselves more vulnerable to climate-related floods, heatwaves and water scarcityAnd it is above all in light of these now well-known results that urban planning is beginning to embrace a new approach.

The role of urban planning

Once upon a time, in the center of Seoul, a highway covered a buried urban stream. As researchers recall in an article on The Conversation, today that same trait has been discovered – a process known as daylighting – and this river is home to plants, fish, and insects. The flowing water refreshes the city in the summer and attracts tens of thousands of people every day, boosting the local economy and the well-being of the community.

Similar transformations are taking place elsewhere. The study considers some specific cases, including the reconstruction of river habitats and wetlands at Christchurch, in New Zealand, and the integration of nature-based rainwater harvesting systems in Vancouver, in Canada. Each of these major projects highlighted critical challenges in urban water planning, but also provided important lessons.

In cities like Breda, Los Angeles and Nanjing, they explain,

Planners don't work alone. Local residents and indigenous communities, ecologists, engineers, and even schools are often involved from the beginning. Together, they bring diverse knowledge of the local context and can build shared environmental management.

The new approach is based on a greater understanding of how water behaves and how this shapes urban habitats, in a process of knowledge sharing that aims to break down barriers between planning, ecology and engineering.

There are still large gaps in our knowledge. How much space do urban rivers really need, and how does this vary from place to place? Which nature-based solutions work best in different landscapes? Urban planners can help answer these questions by learning from what works and using that knowledge to improve freshwater biodiversity outcomes.

The researchers conclude: Cities could become centers for freshwater restoration and recovery, rather than catalysts for decline.

Here are three insights that might interest you:

Flowers all year round: how parks and gardens save bees
Ecological design: how city parks are changing
Geodesign and Ecosystem Services: An Experiment in the Czech Republic