Earth, Population, and Zoonosis

COVID-19 is the latest of many zoonotic diseases that have reached epidemic or pandemic levels in recent decades, including SARS, Ebola, avian flu, and swine flu. Zoonoses are diseases that result from viral animal-to-human spillovers. These spillovers are predominately linked to human encroachment into animal habitats and ecosystem disruption through human activities and climate change.

Zoonoses are increasing due to factors like deforestation, illegal and poorly regulated wildlife trade, antimicrobial resistance, intensified agriculture and livestock production, and climate change. Of the factors that are increasing zoonoses, the following are caused in large part by human population growth:

  • Deforestation
  • Intensified Agriculture
  • Climate Change

Deforestation, along with crowded livestock farming and climate change, is among the main drivers of increased virus transmission from animals to humans. The production of cash crops (crops produced for commercial sale rather than personal consumption) typically involves deforestation, which results in biodiversity loss. This includes the production of key agricultural products such as:

  • Beef
  • Palm oil
  • Coffee
  • Cocoa

Globally, some of the main regions where key agricultural products like beef, coffee, cocoa, and palm oil are produced include parts of sub-Saharan Africa, Southeast Asia, and Latin America. The economies of these regions are largely export-led, which means they react to the overwhelming demand for these goods from North America, China, and Western Europe. For example, over 95% of the coffee and cocoa produced in developing regions is exported to affluent regions throughout North America and Europe.

Brazil as a Case Study

The agricultural sector is one of the most important sectors of Brazil’s economy. Agriculture makes up 4.4% of Brazil’s annual GDP and employs about 10% of Brazil’s entire workforce. Brazil is a leading producer of coffee, sugar, soybeans, and beef. Agriculture and deforestation account for about 70% of Brazil’s emissions.

The environmental degradation caused by intensified agriculture and the production of cash crops leads to the loss of large, predatory animals first. Without predators, the world’s most common zoonotic vectors, including bats, rats, and mosquitoes, are left to multiply. Natural resource depletion increases the competition for dwindling resources. As a result, vector species are pushed further and further into communities and urban areas in search of food and shelter. This forces animals to come into closer contact with humans.


As Kelly Austin, an Associate Professor in the Department of Sociology and Anthropology at Lehigh University, says:

“It is time to connect the dots. Global infectious disease pandemics like COVID-19 and others are the indirect result of a global economic order that depends on unequal access to power and resources. While environmental harm is localized and thus out of sight for most consumers, the consequences are not. They are far-reaching and, as we now know, potentially deadly.”

Deforestation and intensified agriculture are leading to an increase in zoonoses, making the likelihood of a future zoonotic pandemic possible. Population growth and the economic demand for cash crops is driving deforestation and intensified agriculture. In order to reduce the likelihood of future zoonotic pandemics, it is critical to address rapid human population growth and the resulting demand for cash crops and lumber.

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