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Sounding the alarm: Half of Earth’s species are experiencing rapid population decline

The remarkable diversity of life on our planet is in grave danger, with research indicating that nearly half of all animal species are currently in decline. 

This alarming revelation comes from a comprehensive study conducted by Queen’s University Belfast (QUB), shedding light on a troubling trend of eroding biodiversity on a global scale.

The team, led by PhD student Catherine Finn, Dr Daniel Pincheira-Donoso from QUB’s School of Biological Sciences, and Dr Florencia Grattarola from the Czech University of Life Sciences, analyzed the population densities of over 70,000 animal species, compiling what’s now considered the most extensive record of its kind to date. 

The findings, published in the journal Biological Reviews, reveal that 48% of the species are undergoing population declines, while fewer than 3% show signs of increase.

Species evolution and extinction are natural processes, a fact undisputed by scientists. In the history of life on earth, 98% of all species that have ever existed are now extinct. Yet, the speed at which extinction is currently occurring is cause for alarm. 

The sixth mass extinction

According to the Natural History Museum, species extinction is happening at a pace between 100 and 1,000 times faster than anticipated, raising the specter of a human-caused “sixth mass extinction.”

Historically, the severity of an extinction crisis is gauged by “threat conservation categories.” Since 1964, the International Union for Conservation of Nature (IUCN) has maintained a “red list” of threatened species, assessing over 150,000 species to date. Based on their methodology, they classify 28% of the evaluated species as threatened with extinction.

However, the QUB team deployed a different analytic approach, focusing on population trends. Their findings suggest that the magnitude of the extinction crisis is much more severe than indicated by conventional methods. The researchers determined that 33% of species considered “safe” by IUCN standards are actually declining towards the risk of extinction.

Researchers issue drastic alert

Dr Pincheira-Donoso underscored the value of their new methodology, stating, “Our work provides a clearer picture that traditional approaches cannot offer. It’s a drastic alert about the current magnitude of this crisis that has already devastating impacts on the stability of nature as a whole, and on human health and wellbeing.”

The term biodiversity refers to the immense variety of life on earth – from animals and plants to fungi and microorganisms such as bacteria. This diversity plays a critical role in sustaining human life by providing essential resources including fresh water, food, and medicines. 

However, these resources cannot be obtained from individual species alone; it is the rich interplay between a variety of animals and plants that ensures our survival.

Plants, in particular, offer invaluable services in shaping the physical environment. They purify the air, regulate rising temperatures, and offer protection against climate change. 

For instance, mangrove swamps and coral reefs serve as natural barriers against erosion from rising sea levels, while common city trees like the London plane or the tulip tree are adept at absorbing carbon dioxide and removing pollutants from the air.

The research from QUB presents an urgent call for humanity to recognize and respond to the escalating threat to our planet’s biodiversity. The rapid decline in animal species, if unchecked, could have dire consequences not only for the natural world, but also for the survival of the human species.

More about biodiversity

Biodiversity, short for “biological diversity,” refers to the variety of life forms on Earth. This variety encompasses the broad spectrum of all living organisms including animals, plants, fungi, and microorganisms such as bacteria and viruses. 

The concept of biodiversity extends beyond the sheer number of species to include genetic diversity within species and the myriad interactions between species in ecosystems.

Here’s why biodiversity is critically important to the planet and environment:

Ecosystem Health and Resilience 

Biodiversity ensures that ecosystems are robust and can recover from disturbances like natural disasters or human-induced changes. A richly diverse ecosystem has multiple species ready to step in if one species declines or disappears, maintaining ecosystem function and stability.

Provision of Essential Services 

Biodiverse ecosystems provide a host of essential services that we often take for granted. These include air and water purification, soil fertility and nutrient recycling, pest and disease control, pollination of plants, and mitigation of climate change impacts. They also provide materials for shelter, food, and medicines.

Support for Human Survival and Well-being

Biodiversity underpins many aspects of human life. Healthy, biodiverse ecosystems provide food and resources, safeguard water supplies, help mitigate climate change, and protect against natural disasters. They also have recreational, cultural, and spiritual significance for many people.

Scientific and Medical Importance 

Many species have been crucial in scientific research, and our understanding of the natural world largely relies on the study of diverse species. Furthermore, countless medications, from aspirin to cancer treatments, have been derived from plant and animal species. By preserving biodiversity, we ensure a vast, largely unexplored reservoir for potential medical breakthroughs.

Climate Regulation

Biodiverse ecosystems play a significant role in climate regulation. For instance, forests act as carbon sinks, absorbing CO2, which helps to mitigate climate change. Oceanic phytoplankton play a similar role, sequestering huge quantities of CO2. 

Conversely, the loss of biodiverse habitats can exacerbate climate change. Deforestation, for example, not only removes these critical carbon sinks, but also releases stored carbon back into the atmosphere.

Economic Value 

Biodiversity has enormous economic value. It forms the backbone of many economies that rely on agriculture, forestry, fisheries, and tourism. According to the World Wildlife Fund, the services provided by ecosystems are estimated to be worth trillions of dollars per year – more than the global GDP.

As such, the preservation of biodiversity is not only a moral and aesthetic imperative but also crucial for the health of the planet and the survival and prosperity of human societies. 

However, biodiversity is currently under threat on a global scale due to human activities such as habitat destruction, overexploitation, pollution, invasive species, and climate change. It’s crucial that we understand and take action to protect our planet’s biodiversity before it’s too late.

More about mass extinction events

Throughout Earth’s history, life has experienced five major mass extinctions, often referred to as the “Big Five.” These events are characterized by the rapid loss of a significant proportion of life on Earth. A mass extinction is generally defined as a loss of about three-quarters of all species in existence across the entire Earth over a “short” geological period of time.

Here are the “Big Five” mass extinctions:

End-Ordovician Extinction (about 443 million years ago)

This first mass extinction event occurred in two peaks separated by hundreds of thousands of years. It resulted in the loss of 60-70% of all species, most of which were marine organisms. This event is believed to have been caused by an ice age and subsequent global cooling.

Late Devonian Extinction (about 360-375 million years ago)

It wiped out about 75% of all species over a span of millions of years, affecting marine life particularly. Its cause is not well understood but may involve changes in sea level and ocean anoxia (lack of oxygen).

End-Permian Extinction or “The Great Dying” (about 252 million years ago) 

The most severe extinction event in Earth’s history, it eradicated about 95% of all species, both marine and terrestrial. It was likely caused by massive volcanic eruptions in what is now Siberia, leading to drastic climate change.

End-Triassic Extinction (about 200 million years ago)

Approximately 70-75% of all species on Earth went extinct, likely due to volcanic activity and subsequent climate change, as well as potentially an asteroid impact.

End-Cretaceous Extinction (about 66 million years ago)

This event, which wiped out about 75% of all species, is best known for ending the reign of the dinosaurs. It was most likely caused by the impact of a large asteroid or comet near what is now Chicxulub, Mexico.

In recent years, scientists have raised concerns about a potential sixth mass extinction, driven by human activity. Unlike previous mass extinctions caused by natural disasters or climate changes, the main drivers of the current extinction crisis are habitat destruction, overexploitation of species, invasive species, pollution, and anthropogenic climate change. 

Current rates of extinction are estimated to be 100-1,000 times the “background” or expected natural extinction rate, a pace that is faster than the extinction rates in previous mass extinctions. If unchecked, the widespread decline of species could have profound implications for the stability of ecosystems and human societies.


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