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Nature-based Solutions and Carbon sinks

As shown in the Net‐Zero Emissions by 2050 Scenario [1] of the IEA, to reach climate neutrality by 2050 part of the emissions will need to be offset with carbon dioxide removal (CDR). In fact, in the Info Kit for Cities is mentioned that “If cities have GHG emissions which cannot be fully mitigated by 2030 due to technological or financial constraints, those so-called residual emissions will have to be compensated”. To deal with residual emissions, carbon sinks are the best option. They consist of remove carbon dioxide emissions through nature-based solutions (such as forests and soils), or/and technological solutions, such as CDR (carbon dioxide removal). Another option for residual emissions that the Info Kit considers are carbon credits, although it recommends to limit them and it will be subject to certain rules (see the info Kits for more information).

URBAN CARBON STORAGE AND SEQUESTRATION, AND SINGULAR GREEN INFRASTRUCTURE

The focus of this thematic area is the carbon sinks and nature-based solutions. The International Union for Conservation of Nature states that “Nature-based solutions (NBS) could provide around 30% of the cost-effective mitigation needed by 2030 to stabilise warming to below 2ºC” [2]. Furthermore, it can cut emissions from changes in land use (including agriculture, forestry and other land uses [3]) by means of the creation of natural carbon sinks for carbon storage and sequestration. NBS can also tackle major societal challenges such as the environmental degradation and biodiversity loss, water security, food security, human health, economic and social development, disaster risk reduction, or climate change mitigation and adaptation.

NBS foster coordination among sectors (e.g. infrastructures, transport, energy water, built environment and environment) and can foster cross-sectoral policies. In Helsinki the use of urban carbon sinks play a key role in emission compensation for its Carbon-Neutral Helsinki 2035 Action Plan, and related actions such as the planning and green areas design (ensuring sufficient green structures in each plot) or the reforestation and conservation of areas and forests in the city. Choosing the right nature-based solution to meet the diverse urban challenges will be the main issue [4], such as: planting trees for cooling down the streets (like in Lyon), vertical green infrastructure (like in Genova), green resting areas or parks (like in UK), shading green structures (like in Valladolid and Izmir), floating gardens (like in Liverpool), community gardens, etc. and the areas could be connected to grey infrastructure (such as green corridors, like in Vitoria).

Also, NBS can be used for community composting, for recycling organic solids (reducing waste diverted to landfills or costs of transport and city waste management), and use the output as fertiliser and for soil amendment in local parks and green spaces within the community area, or sold through municipal buy-back programmes, like in the city of Nitra. The green areas can be used for also filtering water (green filter area, like in Colombia) or air, through urban garden bio-filter, which can reduce PM and pollutants in the air (like in Valladolid).

For the regeneration of areas that are degraded or contaminated (like roundabouts, roadsides, etc.), smart-soils and phytoremediation can be used, like in Washington DC where plants detoxify a range of pollutants in Spring Valley neighbourhood.

Furthermore, with the right choice of plants and maintenance, pollinators can be increased, e.g. pollinator verges and spaces, like in Ohio where an integrated plan to support the 4B’s was implemented to protect birds, butterflies, bees and beauty along roadsides, which are essential to our ecosystems and to agriculture.

WATER INTERVENTIONS

Last but not the least, NBS can be used for climate adaptation, especially for areas that are sensitive to droughts and floods. To tackle this challenges the following solutions can be used:

Figure: Carbon sequestration through urban carbon sinks (trees, etc.) in Los Angeles

References:

[1] International Energy Agency (2021), Net Zero by 2050, IEA, Paris: Net Zero by 2050 Scenario - Data product - IEA. https://www.iea.org/data-and-statistics/data-product/net-zero-by-2050-scenario

[2] https://portals.iucn.org/library/sites/library/files/documents/2020-020-En.pdf

[3] afforestation / reforestation, enhanced weathering, biochar, soil carbon sequestration, blue carbon methods and techniques, ocean alkalinisation, and ocean fertilization.

[4] https://www.sciencedirect.com/science/article/pii/S1618866721003642

LIST OF NATURE-BASED SOLUTIONS IN NetZeroCities:

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Air qualityBiodiversityClimate resilienceGreen areasNature based solutionsWaterCarbon captureTechnology
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