In the wake of a deadly outbreak of CoronaVirus, there was some positive news that Nitrogen dioxide over China has dropped with the coronavirus quarantine, decrease in pollution levels in Indian cities on the day of ‘People curfew’. It is claimed that nature is reclaiming all it lost with reduced human interaction. But the appreciation and concern is more focused on human-environment interaction on the aftermath of the pandemic outbreak and not on the origin of such interaction.
The origin of such infectious diseases like COVID-19 could be traced back to ecosystem alterations by humans at three landscapes. First at the forest level, deforestation, expansion of settlements along forest edges, increasing human-wildlife contact, forest habitat alteration leading to an abundance of vectors (like ticks, mosquitoes) and reservoir hosts (like pigs, bats). Second, changes at agricultural landscapes – involving water diversion, irrigation water stagnation leading to vector multiplication, mixing of domestic and wild species in farms and unregulated meat trade. Third in an urban landscape, where urban and peri-urban sprawl intrudes into forested areas, development of transport facilities, raising the population density close to wildlife areas.
This increased human and forest interface has led to the easy transfer of pathogens (like virus, bacteria) from vector or a reservoir population of domestic farm animals and from there to humans. This is called the Zoonotic origin of diseases. Also evolutionary capacity of virus to rapid adaptation enables it to transmit effectively in domestic and peri-domestic cycles. A well known example is the earlier form of HIV originated in tropical forests, transferred to humans from primates which expanded to other human dominated regions that had weak public health infrastructure and poor disease surveillance.
Evolutionary capacity of virus to rapid adaptation enables it to transmit effectively in domestic and peri-domestic cycles.
Similarly, most Ebola outbreaks occurred in the forest fringe areas. Frequent human contact with wildlife exposed people living there to previously unknown pathogens. Bats have been suggested as a reservoir for Ebola and monkeys contracted the disease and from there to humans. Fruit bats are also important hosts of many pathogens, including Nipah and SARS virus. Possible emergence mechanism of Nipah is found to be fruit cultivation on forest fringes and wildlife trade for human consumption in the case of SARS disease.
The novel SARS-CoV-2 coronavirus that emerged in the city of Wuhan, China, last year and has since grown into a pandemic is the product of natural evolution, according to findings published in the journal Nature Medicine. The findings also revealed that the molecular structure of the new coronavirus mostly resembles the structure of related viruses found in bats and pangolins. The Covid-19 is a classic example of an emerging disease due to wildlife displacements, deforestation and legal and illegal trade. According to the Wildlife Trust of India website, “It is claimed that pangolins were a source of infection, but like other SARS viruses, these animals could be intermediate hosts of the virus originating in some other species like bats. There are also claims that this intermediary role could have been by turtles, one of the most commonly traded species in Chinese markets. “
Hence, there should be renewed focus on forest land use changes and illegal wildlife trade to prevent the emergence of such novel infectious vector borne and zoonotic diseases. This fact emphasizes the greater role of the forest department in forest resource management for balanced ecosystems, monitoring changes in fauna population along forest borders and curbing illegal wildlife trade. Climate change has led to the creation of the perspective of forests as carbon stocks, similarly in this era of raising pandemics forest management should be visualized as a stopgate to disease emergence. The outbreak of corona, though unfortunate, is also a lesson for the importance of forests.
(All Views are personal)
Further Reading http://www.fao.org/tempref/docrep/fao/009/a0789e/a0789e03.pdf