Biodiversity is fundamental to human health. It underpins ecosystem functioning, providing goods and services that ensure our health and wellbeing. It improves the quality of the air we breathe and the water we drink, regulates temperature in cities, and provides medicines, food and nutrients that maintain our health. Biodiversity is indispensable for the planet's capacity to both regulate and adapt to environmental change – especially climate change and natural disasters. It also benefits our health in many other ways: natural environments with diverse biota enrich human microbiota, which modulate our immune systems, protect us from chronic inflammatory disorders, and can improve brain function. Other mental health benefits, such as the calming effect of greenery, birdsong and natural aromas induced by a walk in the woods, should also not be underestimated.

The 2016 Global Environment Outlook (GEO-6) Assessment for the pan-European region identified biodiversity as a key environmental determinant of human health. But many gains in human development over the last century have come at the cost of biodiversity, both within and outside this region – and the later effects of this now cause health problems. Environmental factors that could be avoided or eliminated cause an estimated 1.4 million deaths per year in the region, as biodiversity loss and ecosystem degradation continue. The key regional drivers of biodiversity loss are linked to increased land-use change: agricultural intensification, urbanisation and habitat fragmentation. Other pressures include unsustainable direct exploitation of biological resources, and invasive species. These drivers and pressures affect human health via the reduction of biodiversity, ecosystem services and food quality, as well as via other impacts such as increasing pollution and waste. These latter impacts further undermine ecosystem services and biodiversity, and are in turn aggravated by their loss. The same drivers contribute globally to the emergence and spread of infectious diseases and are estimated to lie at the root of recent pandemics: for instance, habitat loss and fragmentation force wild animals out of their natural habitat and into closer contact with humans, augmenting the spread of zoonotic diseases.

Cross-disciplinary approaches and collaboration will be necessary for addressing these complex inter-linkages between environmental sustainability and human health and wellbeing, and for ensuring coherence. Two such approaches adopted at European and global level are:

• The planetary health approach, which seeks to promote human health by protecting the natural systems on which it depends. It investigates the effects of environmental change on human health and wellbeing, as well as the political, economic and social systems governing those effects.
• The One Health approach, which focuses on addressing health concerns in the animal–human–environment interface. It seeks to bring multiple sectors to communicate and work together towards better health outcomes by designing and implementing joint programmes, policies, legislation and research.

These two approaches are integral to the WHO Europe’s European Programme of Work, aimed at improving protection against health emergencies – including pandemics such as COVID-19 – and facilitating healthy lives and wellbeing through health-promoting local environments. It seeks to ensure that environmental risks affecting both humans and animals are tackled in an inter-sectoral manner, as set down in the 2017 Ostrava declaration at the Sixth Ministerial Conference on Environment and Health, part of the European Environment and Health Process (EHP).