Updated: May 18
Biodiversity provides essential services to human societies, in particular to human health. First and foremost, ecosystems provide oxygen without which no species on Earth could have developed. But they also contribute to many other life-sustaining services, such as air and water treatment. The destruction of ecosystems by human activities is therefore blamed for many diseases and healthcare issues.
It has been estimated that 23% of annual deaths worldwide (approximately 14 million deaths each year) are linked to environmental factors. Among other issues raised by the erosion of biodiversity, the emergence of zoonotic diseases has been widely discussed in the last two years with the outbreak of COVID-19.
This article proposes to discuss more generally the current and expected impacts of biodiversity loss on human health.
The impact of human activities on natural ecosystems is considerable. Since the beginning of the industrial era, about two centuries ago, more than 85% of the world’s wetlands have been destroyed. In the short period 1980 – 2000 alone, 55 million hectares of tropical forests disappeared to be replaced by crops or pasture (for comparison, there are about 600 million hectares of tropical forests in the world today). As a result, wild animals are forced to migrate away from their native environment and live closer to human settlements, causing encounters between wild species and human populations that were not used to cohabit. The problem is that wild animals can carry pathogens unknown to the human immune system. And this is not an uncommon phenomenon: some experts claim that about 320,000 mammalian viruses may exist in the wild and have not yet been discovered and described. Most of these pathogens would not initially be able to overcome the human immune system, but there is a risk that they could gradually mutate, for example by infecting domesticated animals first, before they could reach humans.
These emerging wildlife diseases are called zoonotic diseases, and their number has increased considerably over the last century.
Since 1940, the number of zoonotic diseases has increased dramatically; they now account for more than 2/3 of the world’s emerging diseases. Figure taken from the article “Global trends in emerging infectious diseases”, published in Nature in 2008.
Various factors can increase the risk of being infected by a zoonosis:
As an example, consider the case of the Nipah virus. In 1997, fires devastated parts of Borneo, forcing many species – in particular bats – to migrate, sometimes hundreds of kilometres away, to escape the blaze. Shortly afterwards, in 1998, domestic pigs in Malaysia and Indonesia began convulsing and many died. Some of their farmers became infected and reported severe headaches and seizures. More than 100 people died before the decision was made to kill thousands of infected pigs. This decision probably prevented a deadly epidemic, as the disease is highly contagious and has a mortality rate of up to 75%. It was later realised that bats, which had migrated after the fires, were carriers of the virus and had infected the pigs through half-eaten fruit that had fallen to the ground or through urine scattered in the pig pens.
Therefore, protecting ecosystems not only conserves species, but also contributes to the protection of human health. This may seem counter-intuitive, as one might think that a large number of species would lead to a large number of pathogens that could potentially be dangerous for humans. However, numerous studies have shown the opposite: the more biodiversity there is in an ecosystem, the fewer diseases appear and spread.
Reservoir of molecules and genes for medication
The erosion of biodiversity can also have a less intuitive consequence: the loss of drug potential. Biodiversity is indeed a reservoir of molecules and genes that are essential for the pharmaceutical industry.
Today, it is estimated that:
- 25% of the drugs used in modern medicine were developed by studying the biodiversity of the rainforest;
- 70% of the drugs used to treat cancer, whether synthetic or natural, have been inspired by nature
The current rate of species extinction is estimated at between 200 and 100,000 per year (the low accuracy of this figure is linked to our poor knowledge of the actual number of species in nature). Moreover, some species are disappearing before we have even had the chance to discover them! In addition to the fact that their disappearance hinders our understanding of their evolution, lifestyles and behaviour, these species are all lost opportunities for science to develop innovative treatments for diseases that already affect humans, and for all those that may one day appear…
Respiratory and water-linked diseases
The services provided by biodiversity include water and air purification, mainly through forests, plants and roots. Specific ecosystems, such as wetlands, are crucial for these services, yet they have been massively destroyed since the onset of the industrialisation era. It is estimated that more than one billion people in the world do not have access to safe drinking water facilities, and therefore depend on natural water filtration mechanisms. The conservation of these protective ecosystems is of vital importance to them.
In addition, studies have shown that the quality and degree of exposure to nature and plants, particularly for people living in urban areas, seems to collerate with the development of chronic respiratory diseases, especially in children. Again, the restoration of natural ecosystems worldwide could improve the health and well-being of the world’s population.
Another consequence of the erosion of biodiversity, and more specifically of the loss of genetic diversity in human crops, is the decrease in crop resilience, and the decrease in the nutritional quality of diets.
Originally, each ecosystem produced plant species adapted to local conditions, including pests and extreme climatic events. But the spread of large-scale monocultures, the standardisation of diets and the development of processed foods have replaced indigenous diets and crops, resulting in nutritional deficiencies for one third of the world, and the spread of many diet-related diseases such as diabetes.
Our health and the health of the ecosystems in which we live are deeply connected, but we need to better understand their relationship. The erosion of biodiversity and the many pressures that human activities place on ecosystems lead to encounters between species that were not used to meeting, allowing the spread of new pathogens. In addition to the obvious healthcare issues, our economies are also affected: in 2013, the global cost associated with dengue fever, which was spread worldwide by mosquitoes, was estimated at $8.9 billion.
Experts are therefore sounding the alarm (again): the COVID-19 pandemic we are facing is only the first in a list that could be long and more deadly, if we do not take the necessary measures to restore our ecosystems. And the responsibility does not lie solely with the biodiversity-rich countries of the third world. The Nipah-contaminated pigs in Malaysia were for export (Malaysians are predominantly Muslim). Deforestation in Africa for metal mining, which puts workers at risk of encountering wild animals, enables the production of smartphones sold worldwide. Responsibility is shared – and all stakeholders must do their part.
If you are looking for advice on how to assess and manage the impact of your activities on biodiversity, reach out to Cécile Klinguer ([email protected]), Consultant in Environmental Intelligence at Greenfish.