The coronavirus pandemic has once again illustrated the interwoven nature of our planet and how public health is directly linked to our interactions with other humans and indeed other species. The encroachment of humans into various natural habitats has forced several species into direct and unprecedented contact with humans, thereby heightening our risk of contracting untold infections and diseases. While evidence linking the Wuhan wet markets to the spread of the coronavirus is still being verified, it has been proven time and again that human interaction with the altered natural environment has yielded negative consequences. These developments have laid bare the necessity of limiting the impact of human-induced climate change in order to prevent or at least restrict the damage of future pandemics.
Increased greenhouse gas emissions have accelerated climate change and in turn caused erratic rainfall and droughts in regions vulnerable to contagion. It has been estimated that since 2000, even accounting for uncertainty due to contributions from solar and volcanic activity, human activity-induced warming has been around ±20%. This global rise in temperatures has accelerated the melting of ice caps, which threatens to bring back dormant viruses that have remained frozen for decades. For example, in 2016, in Russia, anthrax was released into nearby water and food supply from permafrost that had thawed from a frozen reindeer; it infected over 2,000 other reindeer and even a few humans in the region.
These dangers have only been compounded by an exponentially growing global population, which is expected to reach 10 billion over the next 35 years. This surge has prompted large scale deforestation in order to increase agricultural output to meet increased demand. According to the World Resources Institute, a mere 15% of the planet’s forest cover remains intact; the rest has been cleared out or exploited and fragmented to levels that disrupt interdependent ecosystems like grasslands, wetlands, and biodiversity that depend on these habitats for survival. Overexploitation has caused a loss of habitat for several species who have been forced to migrate to unnatural habitats in search of food and shelter, which has therefore placed them in contact with other species (namely humans) who they would not have interacted with otherwise. According to the United Nations, 20% of the planet’s plant and animal species are now extinct. This void has created an opportunity for pathogens to thrive in new hosts and in certain cases directly translated to a rise in infectious diseases. In fact, according to EcoHealthAlliance, deforestation is linked to 31% of disease outbreaks.
Against this backdrop, a study published in the journal Proceedings of the Royal Society B reports that carrier species like bats, rats, and other rodents are experiencing a population explosion due to their disproportionately high resilience to environmental degradation and human interference. At the same time, there are fewer larger animals to prey on them due to climate change and increased hunting and logging activity. The dangers of this population increase is underscored by the fact that rodents alone account for more than 60% of all zoonotic diseases.
Furthermore, roughly 60% of newly emerging pathogens come from animals, from which 30% can be directly attributed to changes in land-use patterns, which include deforestation, unsustainable farming methods, development, and resource extraction in otherwise natural settings. Over a third of the Earth’s land surface and three-quarters of all of its freshwater are dedicated towards the cultivation of crops and rearing of livestock. Unfortunately, unsustainable practices of rearing livestock have provided a fertile breeding ground for infections to be transmitted from animals to humans.
For example, when Malaysia began clearing out forests to plant palm trees in 1999, fruit bats were driven to roost at the edge of the forest, which bordered a hog farm. Their droppings fell directly into a pigsty and ended up contaminating at least one pig. From there, it is believed that the virus soon spread among the human population through the handling and consumption of that pig, and thus led to the outbreak of the lethal Nipah virus that killed over 150 people. Similarly, almost every major epidemic over the last two decades—be it SARS, COVID-19, or Ebola—has spread among human beings due to wildlife enduring the strain of extreme climate and habitat loss.
Changes to our ecosystem have also impacted the ability of our own immune systems to cope with such diseases. For example, research by Harvard found that people residing in places with poor air quality had a higher chance of dying from COVID-19, even when accounting for other factors that may influence the chances of death, such as pre-existing medical conditions, socioeconomic status, and access to healthcare. This may be due to fine particulate pollution such as black carbon, sulfates, and nitrates (which can enter deep into the bloodstream and lungs and can weaken the immune system), given that an increase in these elements by just one microgram per cubic meter corresponds to a 15% increase in COVID-19 deaths.
Another study in the PLOS Currents Influenza journal further claimed that warmer winters, which have become more frequent as a result of human-induced climate change, are correlated with a more severe flu season in the following winter. This is because the brief recess offered by the cold for year one relaxes the human body’s natural defences, thus reducing overall “herd immunity,” and allowing the virus to have a greater impact.
Other features of human interference are sudden temperature swings and storms, both of which are known to weaken our immune systems. Similar to the relationship between deforestation and rodent populations, rising temperatures benefit disease-carrying vectors like mosquitoes and ticks, and cause them to spread to areas that might have previously been too cold. A 2008 study in the journal Nature found that nearly one-third of the emerging infectious diseases over the last ten years were vector-borne and that the transmissions matched unusual changes in the climate. For example, several years ago, the Indian state of Punjab experienced periodic malaria epidemics that were attributed to heavy monsoons and high humidity, which provided conducive environments for mosquito breeding and survival, thus illustrating the link between climatic events and the spread of vector-borne diseases.
Therefore, beyond directives to maintain personal hygiene, there is a dire need to implement more long-term solutions to manage these interconnected risks. Reducing greenhouse gas emissions and improving air quality by increasing our dependence on low-carbon energy sources like wind and solar power, especially in cities, can yield significant benefits for fighting both viral and climate risks. Further, curbing deforestation, reducing the demand for animal meat, and facilitating more sustainable agricultural and animal husbandry practices could decrease the spread of zoonotic diseases and safeguard biodiversity. Likewise, authorities must support public health leadership by investing in advanced surveillance systems and technologies that allow for early detection of new pathogenic microbes in order to increase disease preparedness.
Ultimately, infectious diseases and greenhouse gas emissions cannot be contained within a country’s borders and therefore require global cooperation, wherein states must come together to combat climate change in order to address the dual threats of disease transmission and the loss of biodiversity. The current pandemic offers a sobering opportunity for governments to realise that to protect against global health risks, we must first tackle climate change and its root causes. For such an endeavour to be successful, however, we must recognise the delicately held balance between humans, wildlife, the economy, and indeed our planet as a whole. However, this is easier said than done.
To Curb Infectious Diseases, We Must First Curb Climate Change. Here’s Why.
By ignoring the perils of climate change and unsustainable living, we risk compromising our immunity and increasing the severity and frequency of future pandemics.
January 13, 2021
SOURCE: YES MAGAZINE