When landscape architect Kotchakorn Voraakhom was growing up close to a busy Bangkok highway, a parking lot was her playground. She and her friends would spend some of their time digging up a crack in the concrete to help plants grow through it, a rare piece of greenery in an otherwise urban environment.

Bangkok was built on flat agricultural land that could absorb water naturally, but city developers’ fondness for concreting over canals now causes regular flooding on a grand scale, Voraakhom told CNBC by video call.

“In the past, we used to live with water, but nowadays you can’t live with water because (of) the way we developed our city based on cars, based on roads, rather than using the canals. (Canals) are very key to the natural infrastructure, but we destroyed it … and how could the water drain?” she said.

“It’s crazy. We’ve got so many (people) living within the city but we don’t realize that humans only think about humans,” she added.

As CNBC spoke with Voraakhom, she scrolled through images of Bangkok, displaying flooded streets and traffic at a standstill. There’s even a picture of a crocodile being carried across a highway by three men who are knee-deep in water, a photograph she also showed during a 2018 TED Talk in which she explained how the city is sinking at a rate of more than a centimeter a year due to the effects of climate change.

Voraakhom’s childhood experience of helping plants grow through concrete inspired her to pursue her career as an urban landscape designer in the Thai capital, a city which has one of the lowest levels of public green spaces per capita among large Asian conurbations. One way to ease flooding is to add green space designed to absorb rainfall, Voraakhom said, and her landscape architecture practice, Landprocess, is behind an urban rooftop farm at Thammasat University’s Rangsit Campus, north of Bangkok.

“The concept is actually coming from the wisdom of how agriculture, farmers used to deal with rain. So, if they lived in mountainous areas, they actually slowed down the (water) runoff and grew rice for food,” Voraakhom explained.

The 22,000 square meter (236,806 square foot) area has terraces to grow crops inspired by traditional rice farms and slows runoff 20 times more efficiently than a regular rooftop made of concrete. The water ends up in four large retention ponds that can hold more than 3 million gallons, thus reducing the potential for flooding and providing a source of irrigation when needed.

Creating urban environments that work with nature is a focus for Malcolm Smith, global masterplanning and urban design leader at engineering firm Arup. “It’s not good enough just to sustain, in other words, to keep where we are. We have to restore and regenerate, and the natural systems are an important part of restoring our balance and regenerating some of the damage we’ve done (as humans),” he told CNBC by phone.

Arup has created Cities Alive, a series of research and events looking at future urban development, including a “green envelope” concept that looks at how adding green roofs and plants to the tops and sides of buildings could provide “significant” ways to improve the urban microclimate.

The concept includes ideas such as moss walls to attract insects, wet roofs to temporarily store water and help cool buildings naturally, and adding trees to the facades of buildings. These are part of Arup’s approach to “rewilding,” a term that in rural areas refers to the idea of letting nature take its course over a number of years. In cities, Arup defines it as being more about having the urban environment work better with natural phenomena, as Smith explained.

“It’s not necessarily about trying to recreate wilderness, but … for us, it's about creating environments, which allow natural processes to thrive,” he said.

One of Smith’s flagship projects has been the development of London’s Stratford City, which helped the U.K. capital win the bid to host the 2012 Olympic Games. The £4 billion ($5.2 billion), 180-acre expanse of former railway land was transformed into an area with housing, stores and sports facilities, as well as parkland, through which the River Lea runs.

For Solene Wolff, founder of Berlin-based environmental consultancy Highvisioned, “renaturing” is the way she’d describe how urban areas are looking to encourage wildlife to flourish. “This is a very effective strategy to tackle (the) climate crisis with a fairly minimal amount of resources … because this is not technologically-dependent … This really goes into recreating or leaving so much more space to nature than it used to have,” she told CNBC by phone. Berlin itself has been named the world’s third greenest city (see box out) due to its parks and public transport options.

Wolff cited the German capital’s Tempelhof Field, a public park on the site of a former airport, as a place that has been successfully renatured. “Shifting toward less curated (landscapes) and more into wild nature has been very effective … it creates one of the best carbon ‘sinks’ you could ever wish to have,” she states. Wolff said such projects also contribute to improving biodiversity, a current focus for environmentalists and governments because goals set in a U.N. strategy in 2010 to protect wildlife have not been met, according to a report published last month.

Other German cities are also using rewilding as a means of tackling climate change. The “Städte wagen Wildnis” initiative, which translates as “cities dare wilderness,” is a five-year experimental project aiming to increase biodiversity in Frankfurt, Hannover and Dessau-Rosslau, which started in 2016.

“In cities, we actually find more biodiversity than one might think,” explained the project’s Head of Communications Pia Ditscher in an email to CNBC. “Ecosystem diversity and therefore letting cities grow wilder holds the chance of mitigating the consequences of extreme weather events caused by climate change — water can drain away, the air is being cooled and carbon dioxide is bound,” she said.

In Hannover, for example, maintenance work in some parts has been reduced, such as cutting grass or pruning trees. The findings of the project won’t be announced until next spring, but Ditscher said a highlight has been bringing different groups together. “For example in guided tours or co-operations with cultural facilities, like drawing classes in our areas or walks with people of different religious backgrounds, talking about the meaning of nature in religion,” she stated.

While there is certainly a drive by some governments and businesses to mitigate the effects of climate change, creating green spaces in cities doesn’t always come easy. Landprocess worked on the Chulalongkorn University Centenary Park, Bangkok’s first new public park in 30 years, a project that required all of Voraakhom’s powers of persuasion to convince the parties involved that it should go beyond being a recreational space to help the city deal with flooding.

The 11-acre “amphibious” park was created on a slope and water runs to its lowest point, where it is collected in a pond — and the park as a whole can hold up to a million gallons that are used to irrigate it during the dry season.

As for future developments, for Voraakhom, the coronavirus pandemic has been a wake-up call, which will make people “adapt or die” when it comes to climate change. “There is this very strong warning that if you (don’t) change, it is going to harm our humanity … the majority of the way we run our business as usual, it’s still not sufficient. And we haven’t acted fast enough,” she said.

Wolff said that while some technology such as electric cars can help tackle the climate crisis, regeneration of ecosystems needs to be a focus. “We actually really need to enter the repairing stage … (and that) means going through regeneration, and (for) every piece of infrastructure, bridge, city (or), masterplan, there is a repair plan around it (for) our ecosystems.”

Writers: Lucy Handley, Matt Clinch
Design: Bryn Bache
Editor: Matt Clinch
Images: Getty Images, Arup, Landprocess