The environment is essential to human life. It might appear an obvious statement, but its implications are more and more intricated than one could think. The report of the scientific task force put together by Harvard University to study the correlation between pandemic and ecology has cast light on one of them: human health depends on the condition of forest conservations too.
By Carlotta Zaccarelli | YPA Italy
The first news is that we are potentially exposed to other pandemics. We have never been totally safe from this risk.
The second news is that pandemic risk is strictly connected to the protection of the environment.
These are the two pieces of information which open the report of the scientific task force put together by the Harvard Global Health Institute and the Center for Climate, Health, and the Global Environment at Harvard T.H. School of Public Health to identify key points useful to develop studies and global practises to prevent pandemics.
Another fundamental concept which runs through the whole research is “spillover”: it is the transmission of a pathogen from a species to another. The mechanism potentially caused epidemics, which turn into pandemics if the infection spreads across international borders and affects a considerable number of people. Now, according to the Harvard task force, pandemic risk is higher when spillovers involve wildlife and human beings: it is a process more common than generally thought which occurs when people and wild animals come into close and uncontrolled, unplanned contact. In such a context, viruses coming from wildlife meet new organisms which exponentially multiplicate their chances to reproduce and survive. They are prone to attack these new potential hosts, mutating their characteristics to better adapt to theirs – if necessary. Hence, spillover. Hence, epidemics and/or pandemics.
This scenario verifies more and more often because of human activities which negatively alter ecosystems and expand the possibilities of promiscuity between human beings and wild animals. The most dangerous of these activities is climate change. Or better, climate change represents the sum of all anthropic interventions which destroy the environment and has, among its consequences, the probability of increasing the global pandemics risk because it caused the destruction of the natural habitats where wildlife lives. Wild animals are thus pushed to migrate, moving where they find food and shelter. Often, this means getting closed to human settlements, to people. The event triggers spillover mechanisms, whose odds of success are increased by the fact that climate change determines the survival success of more generalist species, which are reservoirs of a larger number of viruses and of more resistant viruses.
Another human action bringing about the risk of zoonotic transmission (that animal-man infection) is the land use change: man modifies, often with ecologically violent methods, the function of lands, the way they are used, their position in the ecosystem. It is a frequent phenomenon: between 1960 and 2019, about one third of the global terrestrial surface has been subjected to land use change. And about a third of the infectious diseases caused by spillovers has been generated by this change. Its most evident and sadly renown form is deforestation.
Many excuses are found to justify the brutal devastation of forest areas. The mostly heard one refers to the necessity of obtaining or expanding agricultural lands. Thus, vast portions of forests are cut or burnt to give space to field cultivated regularly cultivated with industrial methods (poisonous for the environment). As climate change, deforestation is the root cause of natural habitat destruction and of its consequences on wildlife. The borders of damaged forests in particular become places of easier contact between wild animals and people, areas of incubation of potential pandemics. From 1940, more than 50% of infectious disease of animal origin have emerged because of the hunger for new agricultural lands.
Forests are threatened also by the expansion of farming: the vegetation is uprooted to create new grazing lands or new intensive farming facilities. The natural habitats where thousands of wild animals live disappear and these beings move closer to farms, where they find oases of food and shelters. Their viruses find new hosts, organisms easy to infect because of their restricted genetic heritage (which means viruses do not need mutating to adapt to ever new life systems) and because of the poor hygienic conditions they live in. This context favours not only an animal-to-animal infection, but also a wildlife-to-human being infectious transmission through the mediation of farmed animals. It means that viruses coming from wildlife jump first to domesticate animals and, from them, to men. The chances of a successful second jump are high because farmed animals tend to share many viruses with farmed, thus people. Pigs, cattle, horses, sheep, and goats are among the species which share the highest number of microorganisms with the human being: they are perfect vehicles of pandemic infection.
A third cause of deforestation is urbanization. Urban settlements are growing at a very fast rate: in 2020, 56.2% of the world population lived is cities. It is estimated that this percentage will grow to hit 60% by 2030. Forest areas are sacrificed to the growth of human habitats. But the high density of population and the poor hygienic conditions of (especially) certain peripheral neighbourhoods are factors which potentiate the transmission of viral diseases. The situation is worsened by the fact that the new tentacles of urban settlements, built over lands which were wild, are recycled as new habitats by the animals that used to live in those spaces: again, this increases the contacts between wildlife and people, with its consequences.
It is now clear that it is these contacts that must be avoided or carefully monitored to prevent the insurgence of new zoonotic epidemics or pandemics. The Harvard report states it unmistakably. Likewise, it advises the global society and its decision-makers to plan and implement strategies of forest conservation to reduce the risk of pathogen transmission from animal to man. In other words, top scientists are saying that the adoption of policies to protect of forest ecosystems and the habits in them is of the uttermost importance for the general medical good. The action limit pandemic risk. Another type of measures aimed at the same goal is ecological interventions. The use of natural enemies to contain the populations of the wild animals more likely to be the origin of spillover effects or the conservation of wetlands which work as natural borders between wild and farmed animal or human settlements are two good instances of such ecological strategies.
The team of the US University stress that these measures have to be global: all the world has to be involved in their formulation and realization. If the protection of the environment calls for urgent actions especially in those areas where ecological policies are more incomplete (tropical regions above all), all countries must make a considerable effort to reduce greenhouse gas emissions, to prevent natural habitat destruction in their territories, to limit the expansion of agriculture, farming and cities. It is essential that all countries make a bigger effort to monitor anthropic interventions over nature and the consequences of the contacts between wildlife, people, and domesticated animals. It is a matter of international cooperation and of global strategies of pandemic risk containment. They are more urgent than ever, given the related alarming numbers.
First off, the numbers of the still unidentified viral pathogens. Scientific projections estimated that the species of virus still unknown but members of the main zoonotic viral families (that is, the groups of viruses theoretically able to spill over to man) are 1.67 million. Among these species, the viruses potentially able to infect the human being amount to a something between 631 thousand and 827 thousand. It means that there are about 730 thousand viruses ready to spread among people and cause an epidemic of which science does not have a single clue. The data is to be contextualised: globally, the emerging infectious diseases have grown in number in the last fifty years and 50% of them have been caused by virus spillovers. This translates into an ever-increasing pandemic risk.
And if this is not enough, there are the numbers of economy. Investing in pandemic prevention strategies on a global level (which include environment conservation policies) means avoiding immense financial and commercial losses too: for example, Covid-19 will cost 4 trillion dollars in term of global GDP. Spread over a century, we have lost 40 billion per year. The international budget for spillover prevention activities amounts to a mere 4 billion per year nowadays: it is a tenth of the economic damage caused by the still ongoing pandemic. Surely, it is not enough to save millions from absolute poverty.
Two were the information opening this reflection on global health and environment. Two are the conclusions drawn from it. The protection of the Planet is a question of global public health: the wellbeing of nature prevents the insurgence of epidemics and pandemics. Hence, the protection of the environment proves once again to be a necessary condition of human life.
We must become fully aware of that and act in consequence. Now.