High biodiversity can reduce the risk to human health. Photo / 123RF
High biodiversity can reduce the risk to human health. Photo / 123RF
In the middle of the coronavirus crisis, many of us have turned to nature to reduce stress levels, improve mental health and stay physically active. Yet, human interaction with nature and ecosystems contributed to the existence of the current pandemic in the first place. So what can we take away from this?
Human action has altered our planet, from land to ocean, and has led to a loss of ecosystems. There is strong evidence that the emergence of zoonotic diseases – those that jump between animals – is linked to alteration of ecosystems and human encroachment into wildlife habitats, and the United Nations has recently linked environmental degradation to the emergence of pandemics.
There are two main ways that our impact on the environment is increasing the threat of pandemics such as the current coronavirus outbreak.
First, with growing human settlements and land-clearing for agriculture, the transition zones between different ecosystems have grown. This leads to species from different habitats mixing and interacting with each other in new ways. These new contacts provides new opportunities for diseases to jump between species, as coronavirus did.
The second important driver for the emergence of zoonotic disease is biodiversity loss. With decreasing biodiversity, disease vectors – those animals that carry and transmit an infectious pathogen – are more likely to feed on vertebrates than other species which are no longer as abundant. Those other species then become the primary reservoir of the pathogen.
An example of this is the increased risk of Lyme disease to humans in North America. It was shown that forest fragmentation led to reduced diversity of vertebrates and increased the abundance of some generalist species such as the white-footed mouse, which has become the primary reservoir of the bacteria causing Lyme disease.
High biodiversity, on the other hand, can reduce the risk to human health. The underlying mechanism is called "the dilution effect" and it works by reducing both the relative density of animals that serve as a natural reservoir for pathogens and the population density of the pathogen vectors (such as ticks). This means fewer encounters between vectors and the animals they infect with the disease.
The benefits of nature
But greater contact between humans and their environment has been one of the most important responses to the pandemic, from a mental health perspective.
Many of us who have been fortunate enough to live in areas where lockdown restrictions still permitted outdoor activities turned to walking and exercising outdoors and enjoying the beauty of rivers, urban green spaces and forests, all the while adhering to the prescribed regulations on physical distance and group size.
As we respond to the pandemic, the draw of such spaces for improving well-being cannot be overlooked. Science has long established that access to urban green areas such as parks and lakes has positive impacts on health, typically due to improved air quality, increased physical activity, social cohesion, and stress reduction. It has also been shown that interaction with nature helps us to better recover from stress.
Greening cities not only supports human health but comes with a wide range of other benefits: it is economical, helps reduces the heat island effect in a time of increasingly extreme temperatures and improves air quality.
Green areas can also contribute to flood risk reduction by allowing more water to infiltrate into the soil and thus reducing the amount of excess water during rainstorms. Finally, urban green can create new habitats for plant and animal species.
What we can do next
In light of this, my hope is that the coronavirus pandemic will instigate action to address the underlying drivers of disease emergence, including ecosystem degradation and biodiversity loss. The challenge of protecting the environment in an era of a rapidly escalating climate crisis is enormous and individuals often feel overwhelmed and unable to contribute to change.
But our recent positive experiences with the environment also present a unique opportunity to emerge from the pandemic with a better relationship with nature. Recognition of the value of green spaces should be encouraged long after the pandemic has passed and, if managed properly, could encourage action on the community level to protect ecosystems from further human incursions.
As we look to the future, growing cities need to prioritise existing green spaces and build new ones within existing city boundaries. Green areas within cities support health objectives without degrading biodiverse areas elsewhere. Experiencing nature outside cities will remain important to maintain human health but will only be possible to access and experience in the long run if we can find a healthy balance between our resource use and nature protection.
Enforcement and strengthening environmental regulations to protect or restore biodiverse areas will be vital. The cost of managing those areas for biodiversity conservation and recreation is easier to communicate if the full range of benefits are considered, including the contribution they make to human health.
A green strategy that helps us build back better after coronavirus can support sustainable development on many accounts, not only for mental and physical well-being, but also to ensure that multiple global goals, such as combating climate change and reducing natural hazard risks, can be achieved.
Zita Sebesvari is the Head of Environmental Vulnerability and Ecosystem Services at the Institute for Environment and Human Security (UNU-EHS) at the United Nations University.
