Recap: Nature-Based Solutions, Carbon Sequestration and the Built Environment

When speaking of nature and biodiversity, cities are not frequently the focus. Yet, built environments are just as important in the fight against climate change. The importance of implementing innovative actions and strategies cannot be over-emphasized. Nature-positive cities can add to biodiverse ecosystems and act as carbon sinks, contributing enormously to climate mitigation through nature-based solutions. Many discussions at COP28 on landscaping, engineering, planning and design around the built environment introduced creative solutions to contribute to net zero. Cities and urban spaces must play their part in the global fight against climate change.

As Johan Rockström from the from the Potsdam Institute for Climate Impact Research explains, "each City on planet Earth today is connected with all the neighbors so that what happens in Rio de Janeiro is also connected to what happens in Copenhagen or Stockholm. We are all connected, through the atmosphere, through the chaological cycle, we're talking about the Global Commons."

During a panel on ecosystem restorations in nature-positive cities, from a strategic and policy perspective, mayors and city leaders spoke of the UN Generation Restoration Cities Project and the choices made that will create a legacy of climate action for years to come. Along with city planning strategies such as walking and bike paths, emphasis was also placed on the impact of arts and culture by Katja Dörner of Bonn and preservation of wildlife within the city by Ekrem İmamoğlu of Istanbul. "Now more than ever is the time to amplify the narrative that parks, open space and nature are vital infrastructure to the health and wellness of our city, just as important as bridges, highways, aviation and buildings. It's the one thing that got us through and out of the pandemic; the one place the world could go to during this awful time in our world history was our open spaces," said Anthony Paul Diaz of Seattle.

Robert Spencer from AECOM introduced the Playbook for Nature-Positive Infrastructure Development, created in partnership with the World Wildlife Fund and the International Federation of Consulting Engineers. The playbook uses the Kunming-Montreal Global Biodiversity Framework to emphasize the importance of integrating nature-based solutions into infrastructure design and discusses conserving and restoring natural ecosystems by proposing some solutions, such as green roofs, living walls, solar gardens and constructed wetlands. Anusha Shah of the Institution of Civil Engineers then spoke of the shift from being nature-sympathetic to nature-positive, where engineers must work with nature and protect nature an asset, using traditional Indigenous knowledge of materials to create inclusive designs.

Landscape architects and engineers advocated nature-based solutions, which have the potential to sequester 30% of greenhouse gas emissions by 2030, to promote resilience and biodiversity in ecosystems in the built environment. Carbon sequestration is an important method of reducing the amount of carbon dioxide in the atmosphere, and there are many opportunities to do so in the urban environment. Nature-positive landscapes are the foundation of terrestrial ecosystems and efforts to achieve 30x30, restore global ecosystems and protect biodiversity. Healthy, biodiverse landscapes that store carbon in trees, plants and soils in turn increase resilience to climate impacts.

There are many opportunities to repurpose, reuse and reconfigure materials that already exist onsite in a low carbon way, transforming spaces into wetlands and recreation areas that can even adapt to rising sea levels in the future. This is the type of resilience the speakers were advocating, by transitioning spaces that are underperforming into carbon sequestration environments for generations to come. Aside from the environmental benefits, accessible public landscapes, such as parks and recreation areas, provide proven physical and mental health benefits that reduce healthcare costs and increase community cohesion. Pamela Conrad of Climate Positive Design noted that, by using cement substitutions in the concrete, lower body carbon materials like wood, adding more plants and trees rather than paving, a courtyard that would ordinarily have taken 200 years to offset its carbon footprint could have only taken 20 while performing to the same level it was meant to.

Protecting and restoring forest wetlands and mangroves not only sequesters carbon but also safeguards against extreme weather events acting as a frontline defence in climate adaptation. A presentation on storm surges and floods on urban coastlines was shown with a belt of healthy mangroves and a village or a city with people and their assets behind it. When there is a storm surge, those mangroves act as a natural frontline barrier, protecting the village and the people. Without the protection offered by the mangroves, had they been removed or been degraded due to climate change, the same storm or flood would cause significant damage to the coastlines and cities.

Nearly 75% of the world's emissions come from the urban built environment and 35% of that from outside of the buildings. In 2018, according to the Nature-Based Infrastructure Global Resource Center, nature-based infrastructure is 42% cheaper on average and creates 36% more value than relying only on gray infrastructure when avoided costs and co-benefits are taken into account. However, despite the immense potential and benefits of nature-based solutions, many stakeholders and decision-makers are not fully aware of the efficacy and value of these solutions, resulting in limited funding and support. A 2021 report from Finance Earth found a $700 billion annual financing gap in nature investments overall.

A similar panel on design, global standards and integrative solutions for a net zero built environment explained that the built environment creates 37% of energy related greenhouse gas emissions. Design thinking can offer integrated solutions for equitable and resilient zero-carbon communities. For example, the Harvard University Science and Engineering Complex in Boston combines passive heating and cooling ventilation, storm water collection, reuse of reclaimed building materials, and a biodiverse landscape and greenway to achieve a 75% energy reduction in comparison to a typical laboratory building.

Sustainable forestry was also discussed, using as an example T3, a mass timber building project that uses the three core principles of Timber, Transit and Technology. There are many T3 projects completed, under construction or in development all around the world; T3 Minneapolis was completed in 2016 as the first modern timber building to be built in the United States in more than 100 years, T3 Collingwood in Australia was completed in 2023, and T3 Bayside and Sterling are in planning stages in Canada. Timber is one of the planet's most rapidly renewable resources and stores carbon rather than emitting it, meaning T3 buildings act as carbon sinks. It is recyclable, biodegradable, nontoxic, and produces less waste than concrete and steel. The timber is ethically sourced from sustainably managed forests, using only young trees as opposed to old growth, and helping to thin out crowded forests and reduce deforestation, and T3 Collingwood features a rooftop solar array that utilizes a renewable energy source to power building services. The project strives to achieve a dual emissions reduction impact, cutting carbon during the construction phase by as much as 40% and then also once operational, targeting net zero emissions.

Often overlooked, the role cities can play in protecting nature can make a tremendous difference in climate action and adaptation. The shift in prioritizing nature-based infrastructure over gray infrastructure significantly affects carbon sequestration and the road to net zero. Many creative innovations have been brought about in order to improve urban spaces and the built environment with the ultimate goal of meeting the targets of the Paris Agreement. Cities have as much of a role to play as nature in the road to 1.5°C, and it must be done together.