Concrete and steel – or mangroves and forests? When it comes to climate adaptation, nature is much cheaper

Concrete and steel structures are often chosen for protecting against climate change, with seawalls, dykes, dams and drainage systems being the go-to solutions. However, these man-made assets are costly and inflexible, unable to adapt to the changing climate. Mangroves, forests and urban trees present a much cheaper and more resilient alternative, offering protection against floods, droughts, rising seas and heat.

Research demonstrates that green infrastructure is cost-effective and functional, providing a high-performance critical infrastructure, unlike grey infrastructure. Mangrove forests can shift as sea levels rise, while green infrastructure proves functional and cost-effective in various nations. Despite the proven effectiveness of nature-based solutions, adoption could be broader if authorities consider them as infrastructure options.

The limitations of concrete and steel arise from their design for a stable climate that no longer exists. As extreme weather events increase, the failures of traditional infrastructure become more common. Living systems like mangroves and forests can adapt to changing patterns of temperature, rainfall and sediment deposition rather than simply failing.

A prime example is New York City's investment in protecting forests and plants, which avoided the need for a conventional filtration plant that would have cost $8.6-11 billion. Mangroves protect coastlines, especially in tropical nations facing the most significant risk from sea level rise. The natural protection of existing mangroves is worth an estimated A$1.2 trillion over 100 years, with planting mangroves costing less than 50% of the grey infrastructure alternatives.

Forests play a crucial role as water infrastructure, filtering rainwater, recycling it, and generating rainfall, with the Brazilian Amazon rainforest's value estimated at $20 billion a year. Urban areas benefit from tree planting, as street trees and urban forests cool cities, reducing heat-related deaths and energy demand. Green corridors along roads and waterways in Colombia have reduced average temperatures by 2°C, saving $1.7 in avoided health costs for every $1 spent.

Challenges remain in implementing green infrastructure, as investment remains limited and traditional grey infrastructure often favored due to established engineering standards and contractual certainty. To overcome these hurdles, governments, climate adaptation funds and development banks must adopt four key changes: recognize green infrastructure as a capital asset, protect existing green assets, include ecosystem value in project appraisals, and integrate both grey and green infrastructure in large development plans for future climate scenarios.