In 2015, much before the COVID-19 pandemic engulfed the world, Professor Sir Andy Haines, Chair of the Lancet-Rockefeller Foundation Commission on Planetary Health, underscored the importance of environmental conservation in human health, while writing the preface for the WHO, CBD and UNEP report, titled Connecting Global Priorities: Biodiversity and Human Health: A State of Knowledge Review. He had cautioned: “The last 50 years have seen unprecedented improvements in human health, as measured by most conventional metrics. This human flourishing has, however, been at the cost of extensive degradation to the Earth’s ecological and biogeochemical systems. The impacts of transformations to these systems; including accelerating climatic disruption, land degradation, growing water scarcity, fisheries degradation, pollution, and biodiversity loss; have already begun to negatively impact human health. Left unchecked, these changes threaten to reverse the global health gains of the last several decades and will likely become the dominant threat to health over the next century”.
Environmental degradation and zoonotic diseases
There has been an increasing recognition that anthropogenic environmental degradation is increasing the risk of emerging infectious diseases in humans. About three-quarters of such diseases are zoonotic in origin i.e., the causal pathogens originate from animals, mostly from wildlife.
The COVID-19 outbreak is one among the many pandemics that have been triggered by human–animal interactions. The destruction of habitats of wildlife and subsequent scarcity of prey/food in their natural habitats forces them to invade human habitations thereby bringing wildlife close to the human populations. Many other pathogens transmit to humans by consumption of wildlife as meat or medicines. Examples are galore that range from plagues (Yersinia pestis bacterium associated with rats Rattus spp., which cohabit with humans), HIV had its origin from the butchery of wild chimpanzees (Pan troglodytes) as meat, and H1N1 influenza virus passed from infected pigs to humans at a meat production facility in Mexico.
Although several wild animals are the reservoirs of SARS-CoV viruses, the exact source of SARS-CoV-2, the causative virus of COVID-19 pandemic, is not yet confirmed. Chinese horseshoe bats (Rhinolophus sinicus/ R. affinis; Order Chiroptera) and pangolins (Manis javanica; Family Manidae) are believed to be intermediary hosts of SARS-CoV-2 virus as shown by Kristian G. Andersen et al. in their 2020 paper, The proximal origin of SARS-CoV-2 (Nature Medicine), Y. Wan et al. in their 2020 paper, Receptor recognition by the novel coronavirus from Wuhan; an analysis based on decade-long structural studies of SARS coronavirus (Journal of Virology), and Robert A. Montgomery and David W. Macdonald in their 2020 paper, COVID-19, Health, Conservation, and Shared Wellbeing: Details Matter (Trends in Ecology and Evolution).
The disease, first reported from Wuhan city of China, is linked epidemiologically to the Hua Nan seafood and wet animal wholesale market in Wuhan. At one such market in Malaysia, for instance, animals were host to 19 bacteria, 16 parasites and 16 viruses that could be passed to people through human–animal interaction and initiate epidemics.
Spiraling impact of Environmental degradation
Environmental degradation due to soil, water and air pollution, land degradation, habitat fragmentation, deforestation, soil erosion, and desertification leads to loss of biodiversity which in turn destabilises the ecosystem structure, function and processes, thereby reducing its ability to provide ecosystem goods and services (i.e., benefits that humans derive from the ecosystem), which are vital for human wellbeing. Ecosystem degradation, such as eutrophication caused by excessive nutrient accumulation in wetlands, reduces water quality drastically. Consumption of such water causes serious human health hazard, particularly affecting children and the poor.
Biodiversity loss and human health
The linkages between biodiversity and human health are well established. For example, the species and genetic diversity provide food, nutrients and medicines. Biodiversity provides services such as water and air purification, pest and disease control, sequestration, and pollination. Air and water pollution can lead to biodiversity loss and have direct impacts on health. The drivers of biodiversity loss, e.g. land-use change, fire, habitat loss, over-exploitation, pollution, invasive species and climate change affect human health directly, or indirectly through impacts on biodiversity.
With the available information, the linkages among biodiversity, ecosystem stability, and epidemic/ infectious diseases such as Ebola virus have been established. The biodiversity, nutritional diversity and health are closely interconnected, and therefore it has been argued that the former two are essential to reduce the impact of pandemics.
The human microbiota i.e., the microbial communities present in gut, skin, respiratory and urino-genital tracts, contribute to human nutrition. These microbiota are further modulated through the use of medicinal plants based on Ayurveda or other traditional health care systems, thereby providing much needed prophylactic immunity against the infection during a pandemic. Environmental degradation would lead to the loss of such biodiversity elements as useful medicinal plants or microbial diversity, scarcity of which would weaken the immune system of humans, exposing them to the greater risk of infection during a pandemic.
A healthy, biodiversity-rich ecosystem has tremendous ability to purify the air and thus provide respiratory health benefits to millions of people. Pandemics such as COVID-19 often attack the respiratory tract and lungs. A healthy lung can better fight the pathogen than a weak or partially damaged organ. Air pollutants such as CO2, NO2, SPM 2.5, SPM 10 and SO2 have serious adverse impacts on the health of the lungs. The loss of biodiversity reduces its ability to ameliorate air pollution, thereby negatively affecting human lungs and respiratory tract, making them susceptible to pandemics.
Strategies to reduce the risk of future pandemics
A country-level strategic plan for post-COVID-19 recovery must be prepared, prioritising adequate preparedness for possible future outbreak of epidemics/pandemics. Besides addressing the problems of economic recession caused due to pandemic, an effective surveillance and response system for early detection of pandemics, saving the life of critical patients, and halting pathogen transmission, must be in place. Environmental conservation must be an integral component of the upstream planning strategy.
While planning for conservation of environment, natural environments surrounding the human habitations, such as green spaces and forests, must be conserved and new ones created, as they play an important role in human physical and mental health, and overall wellbeing. Besides, they mitigate climate change impacts such as extreme temperatures, and ameliorate air, soil or water pollution. They also lower the risks of disasters caused by extreme weather events such as storm and flood. They also reduce soil erosion and landslides.
The existence of village forests/sacred groves — which are rich in biodiversity and form one of the natural heritages of Indian tradition — has been proved to be the savior of villagers against extreme consequences of climate change. Therefore, community actions to raise greeneries near human habitations must be encouraged. All the point sources of pollution should be stopped through enforcement of laws. Pollution-specific ameliorating measures such as, i) planting the appropriate plant species (CSIR-NBRI Green Planner app is a good database of locally suitable different plants, for mitigating air pollution), and ii) reducing the levels of emission should be enforced to maintain respiratory health of human populations.
The inhibition to consume wildlife meat in most parts of India, and conserving the biodiversity and surrounding environment (as evident from a large network of about three lakh sacred groves throughout the country) are parts of Indian culture since time immemorial, which must be resurrected at community level. This would help conserve our environment, biodiversity, and prophylactic medicinal plant and microbial resources, providing safety to our populations against future pandemics as well as reducing the risk of endemics in the country.
