Building in biodiversity For climate, for health

Our cities: Ecological deserts or biodiverse hotspots? According to the 2019 Global Assessment Report on Biodiversity and Ecosystem Services, around 1 million animal and plant species are currently threatened with extinction. This report finds that the health of the ecosystems we depend on is deteriorating more rapidly than ever, affecting the very foundations of our economies, livelihoods, food security, health and quality of life worldwide. In this Urban Insight report, experts show how urban design can make our cities part of the solution.

The loss of biodiversity, deforestation and desertification poses major challenges to sustainable development and has affected the lives and livelihoods of millions of people.

The way we are accustomed to designing our cities, with paved streets and grand buildings, has proven to be less resilient to the effects of climate change. Removing trees and other vegetation and using impervious materials in urban areas have impaired normal ecosystem functions such as the circulation of carbon, water and vital nutrients.

The lack of vegetation exposes us to pollutants, heat waves, vector-borne diseases and other negative effects of climate change. Rich and healthy ecosystems provide us with many benefits and are vital to our survival. As a result of increased urbanisation, cities have a big impact and can contribute to increased biodiversity.

By interconnecting land use planning, infrastructure, architecture and buildings to find the full potential for maximising ecosystem services in these urban structures, we would be able to increase both biodiversity and well-being”, Tarja Ojala, ecologist and forest engineer.

Preserving natural environments, forests and biodiversity in urban areas is vital for sustaining life and plays a major role in the fight against climate change.

Exactly how are biodiversity and health connected to each other, and what role do ecosystem services play in this? Read on to better understand the true challenges we face due to the loss of biodiversity and the benefits we gain from more a diverse natural environment.

Biodiversity in cities

A necessary reconnection with nature

Climate change has already put our mental and physical health to the test in cities. We have seen how urban structures with paved streets lack resilience to the changing weather conditions: heavy rainfalls and extreme heat challenge the minds and bodies of citizens around Europe.

Ctizens need the diversity of a built green environment, and we who lead Helsinki City must pay attention to it in holistic way: more meadows instead of homogenous grass fields, green roofs for pollinators, more biodiversity and a richer variety of species in parks. The urban structures and built environment have a remarkable possibility to preserve biodiversity.
– Anni Sinnemäki, Deputy Mayor, Helsinki

Genetic, habitat and species richness has long been associated exclusively with rural areas and has even been isolated from the discussion on urban structures. Nevertheless, the natural environment can also exist and thrive in an urban environment. Biodiversity in cities has long been undervalued.

Built environment challenging biodiversity

Urbanisation in its current form is one of the greatest challenges to biodiversity. Urbanisation alters the natural environment, so it becomes an artificial one containing buildings and other impervious surfaces. The fact that urban settlements are concentrated in biodiversity hotspots, like along coastal areas, river deltas and rivers, increases this threat.

Almost 1,700 species in Europe are threatened by extinction and 36 species have already become extinct since 2015. All these species have fundamental value in themselves, but they also benefit human life in many ways. One that has suffered a lot in recent decades is the bumblebee, which also plays a critical role in global food production; 45.6% of bumblebee species show a declining population trend.

Encouraging biodiversity in the garden helps to increase ecosystem productivity.

Biodiversity and nature are more present in our cities and urban spaces than is generally understood. The cities create multiple microclimates that can be used by flora and fauna due to the variation of building structures and their facades. There is more opportunity for flora and fauna to thrive in urban areas than in many rural areas where monocultural arable farming is present as these landscapes often offer little protection. The key to ensuring that cities can thrive as ecosystems lies in ensuring that more species are also benefited through a targeted approach to habitat design.

Nevertheless, cities are currently attracting mostly generalist species, which means that urban planning should support natural diversity in cities providing a place for more original, indigenous species.
Climate change challenges urban health and biodiversity through the adverse effects of extreme heat, health issues related to poor water quality and inundations after heavy rainfall.

Carbon sequestration in soil is disturbed in urban areas where impervious surfaces impair natural cycles of nutrients, water and carbon, further accelerating climate change.

The deterioration of soil is another invisible consequence of climate change, yet still poses a threat to human health. Healthy soil is maintained by microbes, and microbiota influence the human intestine microbiome via direct contact with soil as well as via food. Improving urban biodiversity exposes us to richer environmental microbiota developing our resistance to diseases.

Nature is also beneficial to our mental health. Urban environments can be noisy and have low air quality due to heavy traffic and dense population. Ecosystem services and nearby nature can reduce stress and anxiety and provide benefits for both physical and mental health, when well designed.
A rich soil and root microbiome would have several advantages for terrestrial ecosystems and biodiversity through increased efficiency of nutrient use and uptake, which would improve plant resistance and resilience to global climatic change and biotic stressors. Healthy soils are also able to store carbon in roots and organic matter and prevent flooding.

Ecosystem services – providing health and resilience

Ecosystem services are benefits we humans obtain from the natural ecosystem encouraged by biodiversity. Ecosystem services are divided into four key areas:

  • Provisioning – the supply of food, clean air and water and materials
  • Regulating – water and climate regulation, nutrient cycling, pollination, or the formation of fertile soils
  • Supporting – soil formation, photosynthesis
  • Cultural – recreation.

The resilience capacity of cities increases if their infrastructure is integrated with natural systems, services and resources. For example, permeable surfaces, tree canopies and wetlands regulate water flow much more efficiently than artificial structures. This also reduces the relative probability of infrastructure, such as roads, railroads, buildings and waterways, suffering significant negative impacts from the increasing environmental shocks and stresses associated with climate change.

Ecosystem services – how trees and vegetation help

City trees and vegetation play an important and sometimes unexpected role in supporting human health and well-being as well as in climate change mitigation and adaptation.

Trees and vegetation – above ground

  • Forests remove around 430 million tons of atmospheric carbon dioxide and store 13% of Europe’s greenhouse gas emissions
  • Trees properly placed around buildings can reduce air conditioning needs by 30% and save energy used for heating by 20–50%
  • Trees and vegetation reduce stormwater runoff by capturing and storing rainfall in the canopy and releasing water into the atmosphere through evapotranspiration

Trees and vegetation – below ground

  • One third of a tree’s biomass is below ground in the roots
  • Carbon is stored in the soil: approximately 75 billion tons of carbon in EU soils alone in the form of plant and animal material are in various stages of decay
  • Soil has the potential to offset 5–15% of global emissions

Trees, vegetation and biodiversity

  • Parks and urban forests maintain and increase biodiversity in cities
  • The diversity of tree species and presence of dead wood are the
    key elements for diversified flora and fauna
  • There are 454 native tree species in Europe, of which over 58%
    are native to continental Europe, and of these 42% of the species
    are threatened by extinction
  • Almost a fifth (18%) of European dead wood beetle species
    assessed so far are at risk of extinction due to the ongoing decline
    in large old-growth trees across Europe

Trees and nature – health and well-being

  • Spending time near trees and nature improves physical and mental health by increasing energy levels and speed of recovery, while decreasing blood pressure and stress
  • A mature leafy tree produces as much oxygen in a season as 10 people inhale in a year
  • Conifers are more efficient at capturing small particles from the air than deciduous trees
  • The strategic placement of trees in urban areas can cool the air 2–8°C, reducing the urban heat island effect

Tomorrows housing development – urban recreational spaces. The landscape architecture actively integrates biodiversity in local rainwater management and the meadowy landscape. Design by Sweco.

How can we utilise the built environment as part of the ecological system?

In urban planning, we need to shift focus from merely extracting benefits from the natural world to addressing how we can enhance our world and surrounding environment based on human needs for interaction with nature.

Urban planners should incorporate local and native biodiversity as natural elements that promote well-being to include trees, shrubs and other vegetation, water features, parks and gardens. Vegetation provides nesting and resting places for animals, buffers noise, offers shade, reduces the effect of heat islands, traps particulates and other airborne pollutants, captures carbon dioxide and mitigates global warming. Parks and other natural areas filter groundwater and reduce stormwater runoff and therefore support public safety. When urban planners are able to choose measures that both support biodiversity and increase resilience, this will also benefit people living in cities.

Neighbourhoods of the future, planned to preserve nature. Design by Sweco.

Health benefits

Vital body – benefits for physical health
Exposure to microorganisms in soil, especially at an early stage, benefits the human immune system and can protect us from diseases like asthma and atopy (the tendency to develop allergic diseases). Biodiversity plays a role in the regulation and control of infectious diseases and provides important resources for medical research, for both traditional and modern medicine.

Balanced mind – benefits for mental health
There is a growing body of evidence showing that time spent interacting with natural habitats increases mental well-being and decreases the effects of stress.

These benefits include:

  • Improved general psychological well-being
  • Positive effects on emotions and behaviour
  • Positive effects on cognitive function
  • Increased ability to perform mentally challenging tasks
  • Less stress
  • Facilitated social interaction

In addition to decorative qualities and possible food supply, vegetation and flowers help supplement the increasing loss of natural habitats.

What can you do as a citizen?

By mimicking natural processes and favouring species that are native to a biogeographical area, we can create more diverse habitats for animal and plant species and create places for recreation. Most cities also have local nature conservation associations where citizens can do voluntary work to preserve an area’s natural values.

The perfect way to help biodiversity thrive in cities is your very own backyard or a community garden. The four basic needs for wildlife include food, water, shelter and nesting.

Consider what species you want to help and what their food and habitat requirements are. Implement suitable horticulture practices by getting rid of invasive species and cultivating species native to the area. Plant trees and shrubs to provide sources of food and shelter and to sequester carbon. Flowers will attract bees, butterflies and other pollinating insects. Bird and bat houses offer shelter and nesting places for these species, alongside insect hotels, green roofs and walls, urban beehives and wetlands, which are good examples of mimicking ecosystems in the urban landscape.

Future construction planned to protect nature and biodiversity. Design by Sweco.

In summary

Climate change has already put our mental and physical health to the test in cities. We have seen how urban structures with paved streets lack resilience to the changing weather conditions: heavy rainfalls and extreme heat challenge the minds and bodies of citizens around Europe.

One of the consequences of climate change is the loss of biodiversity, which also has significant though more invisible effects on human health. However, we need rich natural environments and ecological services to support well-being on many levels. Healthy ecosystems with healthy soils bring resilience to cities, maintain normal carbon, nutrient and water cycles, and maintain diversified micro-biota.

Traditionally, nature conservation has been put into practice outside cities. But cities are actually part of the answer.

We should pay more attention to connecting the rural biodiversity hotspots to urban ones and mimicking the natural environments in urban structures.
Our land use and infrastructure planning and execution should take a more radical approach going forward. On our way to carbon-neutral and citizen-friendly urbanisation, we should try to save vegetation and soil when and wherever possible, create new habitats inside our cities, restore habitats where needed, use permeable surfaces in construction, and get citizens involved in planning and taking care of their environment.

About the authors

TARJA OJALA is a biologist and forest engineer based in Lahti, Finland. She has a broad understanding of urban ecology, ecosystem services and ecological corridors. Her passion is to spread ecological information to people and communities to raise awareness of how our everyday choices impact our environment and how these impacts can be diminished.

ISHBEL CAMPBELL is an ecologist based in London, UK, with a passion for urban greening as part of building sustainability. Ishbel has 6 years’ experience of urban ecology and she aims to grow the aspect of urban greening within urban design by working with clients and colleagues around the UK and Europe.

Other contributing experts

  • Lt.Gen. Richard Nugee,
  • Anni Sinnemäki
  • Mikko Raninen
  • Martijn Steenstra