Challenges

By 2050, two-thirds of humanity will live in cities. Achieving national sustainable development objectives and the SDGs depends on healthy and resilient cities. Responsible for around 75 percent of global CO2 emissions, cities are also at the forefront of fighting climate change while being particularly vulnerable to its impacts.

Heat extremes, which are increasing under climate change, drive heat-related deaths and reduce worker productivity, while increasing required expenditures on air conditioning, which in turn drives increased carbon emissions. Extreme weather is also increasing the risk and severity of urban flooding and landslides, threatening lives, livelihoods and property. Many residents, often disproportionately those in marginal communities, do not have adequate access to green space, despite its scientifically proven benefits for physical and mental health.

Yet, while cities urgently need to build resilience and deliver mandates across the Sustainable Development Goals (SDGs), they face many legal, finance and capacity challenges, including limited support from national governments.

Toward a Solution

The Trees in Cities Challenge was launched by UNECE in September 2019 at the United Nations Climate Action Summit and aims to make cities greener, healthier and more resilient by expanding sustainable urban forestry.

Sustainable urban forestry is an integrative and cost-effective nature-based solution to these challenges and can help develop greener, healthier, and more resilient cities. Trees and forests in urban and peri-urban areas provide vital benefits for health and well-being, sustainable development, climate adaptation and mitigation, biodiversity and disaster risk reduction. These benefits contribute to many SDGs and other local, national and global ones.

It contributes to achieving SDG15.2 (sustainably manage of all types of forests, halt deforestation, restore degraded forests, increase afforestation and reforestation), and SDG11.7 (universal access to safe, inclusive, and accessible, green and public spaces). The many benefits of sustainable urban forestry also make strong contributions to most SDGs. Examples include:

• Creating and enhancing habitats and contributing to land restoration (SDG 15)
• Creating green jobs and providing ecosystem services (SDG 8)
• Contributing to food security through urban food forests (SDG 2)
• Improving air quality; providing space for healthy lifestyles and mental health (SDG3)
• Cooling the air up to 8°C, reducing health risks of extreme heat (SDG 3)
• Reducing the risk of flooding and mudslides (SDG 6, 11)
• Reducing the need for building heating and cooling (SDG 7, 8, 13)
• Increasing safe, inclusive and accessible green space (SDG 11)
• Increasing resilience to climate change impacts (SDG13)

To achieve these benefits and accelerate the use of sustainable urban forestry to achieve the SDGs and build resilient cities, the Trees in Cities Challenge asks mayors to commit to tree planting pledges, including sustainable urban forestry targets and practices. This approach helps to build political will to expand and strengthen the use of sustainable urban forestry as a nature-based solution. To date, over 50 cities around the world have committed to planting over 12 million trees, of which over 8 million have already been planted.

Yet while there is an urgent need to expand the urban forest cover in urban areas, afforestation and tree planting interventions should be adequately designed and include provisions for sustainable, long-term management. This ensures that the benefits provided by the urban forest are optimized over time.

The initiative has been welcomed by cities and countries, which have expressed interest in maximizing opportunities for exchange or experiences and lessons learned. As a result, participating cities from the Global South and North can now join the Informal Network of Experts on Sustainable Urban Forestry, formed by UNECE in October 2021 building on the success of initial peer exchange events, as a participatory peer learning community where cities exchange best practices and support to overcome the myriad challenges they face as local governments.

This supports the long-term sustainable management of urban forests and trees by participating cities, so that trees are planted in the right place, for the right reasons and grow to maturity so that they can deliver their many co-benefits. The Network also facilitates collaboration on issues of common interest or concern, including ongoing work on benchmarking. The network also includes representatives of national governments, civil society and the private sector, facilitating exchanges across sectors and levels of government, as well as among cities from the Global North and South. Furthermore, discussions during meetings of the Network of Experts have helped inform the drafting of a policy brief on Sustainable Urban Forestry.

Sustainable urban forestry has received limited attention from national ministries and institutions in many countries. By engaging first at the city level to promote sustainable urban forestry, the Trees in Cities Challenge strengthens the capacity of cities to contribute to efforts to achieve national development objectives and the SDGs. At the UNECE level, it has helped to build awareness among policymakers and other key stakeholders at the national and regional level. In particular, the UNECE intergovernmental mechanism on forest and the forest industry included urban forestry in its integrated programme of work, and a regional action plan is currently under development. The integration of the initiative in the intergovernmental context will support its integration in national and regional policy, and thereby not only sustain outcomes of the initiative, but also accelerate and scale up the impact in the future.

A key lesson of the initiative is that the exchange of experiences among cities is particularly valuable. Municipal governments typically have broad mandates with limited technical depth in any given area. Peer networks provide support in the planning, planting and management of urban forests to enhance their contribution to the SDGs. This helps build capacity for effective on-the-ground implementation of sustainable urban forestry. This can be critical because, unlike sectoral ministries, cities have integrated mandates for sustainable development, and so all the co-benefits of urban forestry across the SDGs are relevant to city governments. This can be therefore be an effective approach to localize the SDGs.

The innovative model of the Trees in Cities Challenge initiative – building political will among mayors and supporting implementation through peer networks – can be replicated as an approach to localize the SDGs. The initiative also demonstrates that strong subnational engagement, particularly when complemented by diverse stakeholder networks, can also be an innovative approach to build momentum for – and gather lessons learned and input for – national and regional policy action to sustain and accelerate the development outcomes and enhance regional cooperation in the long term.