Scientists around the world observe the public health consequences of human activity on the environment. The recent coronavirus pandemic has inspired a notable scientific regard in identifying the role of the environment and human activity on the spread of disease. The dominant areas of environmental investigation concern worldwide deforestation, and the loss of biodiversity among species.
Over the last couple of decades, researchers have noticed a strong correlation between the loss of biodiversity among wildlife and the spread of disease. These findings lead scientists to believe that an abundance of diversity within ecosystems protects them against infectious diseases. Felicia Kessing, a biologist at Bard College, published a study revealing the devastating consequences of the exponential population growth on the conservation of species. According to her research, the current extinction rate is approximately 1,000 times higher than the background extinction rate, which refers to the estimated rate of extinction before humans became a main contributor to extinction. It is estimated that the population sizes of all animals have decreased by 30% since the 1970s.
It is speculated that certain species that have lower reproductive rates invest heavily in immunity by acting as a buffer against disease transmission whereas species with higher reproductive rates are more likely to act as hosts of disease. The disease-buffering species, due to their low reproductive rate, are more likely to lose biodiversity or become extinct due to human activity compared to the species that tend to become hosts. According to the World Health Organization (WHO), as diversity among ecosystems is lost the “complexity of the overall system can make it more vulnerable…potentially creating new opportunities for disease emergence and poor health outcomes.”
The orangutans of Indonesia are considered an umbrella species, which are vital to in-situ conservation of other species that share the habitat. They serve a particularly important role in the distribution of seeds that eventually become part of the fauna of the rainforest. However, the orangutan species has become critically endangered due to the alarming and human-induced loss of habitat within rainforests globally.
Due to the loss of umbrella species, such as the orangutan, and the destruction of natural habitats, wildlife has been forced to come into close contact with human populations, often initiating the spread of deadly illness. In 1997, roughly 66 million acres of land were burned in Indonesia for agricultural use. This scorched region of land had previously been a habitat for fruit bats that lived off of the fruit-bearing trees. The destruction of the trees forced fruit bats to migrate within close proximity of humans.
Upon the Indonesian fruit bat population’s migration to rural Malaysia throughout the late 1990s, local farmers and farm animals became severely ill at alarming rates. These fruit bats were carriers of the deadly Nipah virus. According to the United States Center for Disease Control and Prevention (CDC), the Nipah virus is a bat-borne zoonotic disease transmitted from animals to humans through contaminated food. Mild cases typically cause acute respiratory infection whereas severe cases can cause fatal encephalitis which is inflammation of the brain.
Zoonotic diseases, such as the Nipah virus, are responsible for approximately 2.4 billion cases of illness and 2.2 million deaths among human populations every year. The deadly Nipah epidemic resulted in over 200 deaths in 1999 with a mortality rate of approximately 80% and no cure or treatment available. The Malaysian outbreak produced the first known cases of the Nipah virus and served as the origin of recurrent outbreaks across the Southeast Asian region. The outbreak was a direct result of human activity that forced disease-carrying species within the vicinity of human civilization.
Deforestation also has a strong influence on climate change due to the carbon sequestration abilities of trees. The clearing of millions of acres of trees has exacerbated the issue of climate change around the world by allowing greenhouse gases to accumulate in the atmosphere and raise global temperatures.
Research conducted by Stanford Biologist Erin Mordecai predicts that as global temperatures continue to rise due to human activity, the transmission of vector-borne diseases will increase as well. Mordecai’s research primarily concerns the spread of disease by mosquitoes. Mosquitos are transmitters of some of the most fatal infectious illnesses such as malaria, the West Nile virus, and the Zika virus.
Cool temperatures and economic development have substantially deterred mosquito-borne illness from the Northern Hemisphere. However, climate change threatens to change that by allowing warmer temperature spectrums around the world and creating optimal conditions for mosquitoes to transmit the illnesses they tend to carry.
According to Mordecai’s research, malaria is mostly spread at temperatures around 80 degrees Fahrenheit. The average temperature in the Northern Hemisphere rests at about 60 degrees Fahrenheit with climate change increasing by an approximate annual average of 0.14 degrees Fahrenheit.
“If you’re thinking about the impacts of climate change, this tells you a few degrees of warming has a big impact,” Mordecai remarked about the results of her research.
Environmental changes like deforestation and climate change provide an urgent threat to the public health of all life on Earth. The World Health Organization has not found evidence of a direct correlation between climate change and the emergence of the coronavirus, however they believe that the environment has had an indirect effect as “there is evidence that increasing human pressure on the natural environment drives disease emergence.”
Various international efforts have been made to curb deforestation through the conservation of umbrella species. The World Wildlife Fund has been working to save the orangutan since the 1970’s by making efforts to protect the species against poaching and deforestation. However, the rates of deforestation for agricultural and industrial use continue to dangerously outmatch conservation efforts. Unless more widespread efforts to maintain the forest are made, the health of all life on Earth may be threatened with infectious disease.
Sources
Center of Disease Control and Prevention. (2021.) Nipah Virus (NiV). Retrieved March 18, 2021, from https://www.cdc.gov/vhf/nipah/index.html
Gilbert, N. (2010, December 01). More species means less disease. Retrieved March 22, 2021 from https://www.nature.com/news/2010/101201/full/news.2010.644.html#B1
Global Animal Health Association. (2021). Zoonoses. Retrieved March 20, 2021, from, https://healthforanimals.org/zoonoses.html#:~:text=Zoonoses%20threaten%20people%3A%20Just%2013,in%20animals%20safeguards%20our%20health.
Hull, M. (2016, April 06). Save the orangutan, save the ecosystem. Retrieved March 22, 2021, from https://orangutan.org/save-the-orangutan-save-the-ecosystem/
Jordan, R. (2019, March 15). How does climate change affect disease? Retrieved March 24, 2021, from https://earth.stanford.edu/news/how-does-climate-change-affect-disease#gs.x5mugt
Kessing, F. (2010, December 01). Impacts of biodiversity on the emergence and transmission of infectious disease. Retrieved March 26, 2021, from https://www.nature.com/articles/nature09575
Lustgarten, A. (2020, May 07). How climate change is contributing to skyrocketing rates of infectious disease. Retrieved March 21, 2021, from https://www.propublica.org/article/climate-infectious-diseases
Rainforest Alliance. (2018, August 12). What is the relationship between deforestation and climate change? Retrieved March 19, 2021, from https://www.rainforest-alliance.org/articles/relationship-between-deforestation-climate-change
World Health Organization. (2020, April 22). Coronavirus disease (Covid-19): Climate change. Retrieved March 25, 2021, https://www.who.int/news-room/q-a-detail/coronavirus-disease-covid-19-climate-change#:~:text=There%20is%20no%20evidence%20of,transmission%20and%20treating%20patients.
World Health Organization. (2018, May 30). Nipah virus. Retrieved March 18, 2021, from https://www.who.int/news-room/fact-sheets/detail/nipah-virus
World Wildlife Fund. (2021). Sumatran orangutan. Retrieved March 22, 2021, from https://www.worldwildlife.org/species/sumatran-orangutan
Zimmer, K. (2019, November 22). Deforestation is leading to more infectious diseases in humans. Retrieved March 23, 2021, https://www.nationalgeographic.com/science/article/deforestation-leading-to-more-infectious-diseases-in-humans