Loss of biodiversity, a global phenomenon
The research results show that human disturbance has led to an ecological crisis on a global scale.
A study published in Ecology Letters reveals that human disturbances affect the disease dynamics of a place through its effect on the prevalence of host and parasite species in geography, as Mongabay-India reports.
Researchers from the Indian Institute of Science Education and Research (IISER) Tirupati and the University of Georgia, South Carolina, USA, conducted the study in the 600 km south of the Indian Western Ghats, a treasure trove of biodiversity and one of the eight “hottest spots” of biodiversity.
The regions of the Western Ghats have been subjected to severe human disturbance. They are known to house host communities that have become less diverse over time. In many well-characterized host-parasite systems, low diversity communities tend to include host populations that are most competent to harbor and transmit parasites. Parasites retained in disturbed ecosystems are mostly hardy and can infect multiple species, a characteristic that also increases their ability to cause emerging infectious diseases.
Research results show that human disturbance has led to an ecological crisis on a global scale, one of the primary impacts being the loss of biodiversity and the alteration of the community structure of many species. This altered structure of the parasitic community can lead to an increased frequency of outbreaks of infectious diseases, many of which are emerging and re-emerging.
Parasites are important parts of ecological networks and biodiversity. Known as ecosystem engineers, they help shape community structure by influencing host populations in multiple ways and regulating food web stability or “what-to-eat-what in a community.” Thus, the loss of parasitic species can lead to a biodiversity crisis with dramatic impacts on ecosystem health and services, including nutrient and energy cycling, and disease dynamics.
The study authors say that these disturbances could be anything that results from human presence or their activities, for example, how humans use the land they inhabit. “We have found that human disturbances and the structure of the host community affect the structure of the parasite community after controlling the effects of the environment, ie the climate, the terrain,” reports Mongabay-India. Humans continue to alter the environment and encroach on wild spaces, researchers say, potentially contributing to the increase in emerging infectious diseases such as COVID-19 and other zoonotic diseases that spread from wildlife to humans. by altering parasite communities and their host preferences.
The link between increasing infectious disease epidemics and loss of biodiversity has been around for some time, being attributed to the persistence and proliferation of general practitioners. In addition, human proximity to wildlife increases the propensity for transmission of pathogens occurring in nature. Sometimes the pathogen can pass to humans from a non-human animal that it may inhabit, causing a zoonosis. More than half of the pathogenic organisms in humans are zoonotic, with about 13% of the total emerging and re-emerging organisms. A steady increase in zoonotic diseases has been observed in recent times, with India being one of the four most affected countries.
Sampling was carried out in four large geographic regions separated by three biogeographic barriers which are mostly isolated and show no record of disease prevalence and modes of transmission. Large parts of these areas lie beneath the network of protected areas, however, fragmented human settlements are uncovered, paving the way for analysis of the effects of human disturbance in otherwise isolated areas.
The authors elucidate how climate, habitat, and human disturbance affect parasite prevalence both directly and indirectly through their effects on host diversity. They emphasize that there is a critical need for conservation and public health policy experts to work together to ensure healthy ecosystems conducive to healthy human and wildlife populations.
The Mongabay-India report indicates that biodiversity loss is accelerating globally and locally with around one million species threatened with extinction, according to the 2019 Global Assessment Report on Biodiversity and Ecosystem Services, argued by the United Nations. Extinctions, however, are not random. Some species are extremely vulnerable to extinction while others are not. In free species, or species that do not depend on other organisms for their survival, specialists are more sensitive to environmental disturbances than generalists. Specialists are organisms that feed on a narrow diversity of resources or habitats, while those that acclimatize to a wide variety of resources are called generalists. Likewise, there are specialized parasites which infect only one or a few related host species and generalist parasites which prefer to inhabit a wide variety of hosts.
Experts around the world suggest a cross-sectoral (One Health) approach to mitigate the challenge posed by increasing biodiversity loss, especially in the case of zoonotic diseases.