Scientists have identified and named over a million animal species, with millions more yet to be discovered across Earth’s seven continents. But which continent holds the record for the most animal species? The answer, according to experts, is South America.
For centuries, scientists have been cataloging and geolocating species around the globe. Before the digital age, most species distribution data came from museum collections, explained Vítor Piacentini, an ornithologist at the Federal University of Mato Grosso in Brazil. Nowadays, public contributions have significantly bolstered this effort.
In the past two decades, there has been a “revolution” in citizen science, Piacentini told Live Science, with scientists using data collected by the public to fill knowledge gaps. This influx of information has allowed scientists to map the global distribution of species more accurately.
In the late 1980s, scientist Norman Myers introduced the term “biodiversity hotspot” to describe areas with an exceptionally high number of species relative to their surface area. Currently, 36 such hotspots are recognized worldwide, most of which are located on continents that cross the equator, where the climate is warm and humid.
This high biodiversity is not only due to animal populations but also to plant diversity. Plants are the foundation of species,” said Barnabas Daru, an applied ecologist at Stanford University. “If a place has a higher diversity of plants, it makes it easier for other organisms that depend on those plants to become more abundant.”
While plants can thrive in various conditions, they generally flourish in warm, humid environments. The combination of humidity and warmth provides essential moisture, with warm air trapping water molecules to create humidity. Warmth also benefits many microorganisms, particularly decomposers, which break down dead material, enriching the soil for plants.
Additionally, insects, crucial for pollinating flowering plants, thrive in warmer climates because they cannot regulate their own body temperature. More insects in the tropics lead to more pollination and more food for predators, explained Daru.
Piacentini emphasized that other factors also contribute to high biodiversity. A continent must offer not only tropical conditions but also a variety of habitats. Regions with high biodiversity have many potential niches for animals to occupy. For instance, tall trees or high mountains create vertical variation in temperature, sun exposure, and terrain, allowing more species to coexist without direct competition.
Based on these factors and data from museums and citizen science, most scientists agree that South America boasts the highest number of animal species. The continent’s Amazon rainforest, with its four-layered tree canopy, and the Andes mountains, with numerous microclimates, provide an ideal combination of heat and diverse geography. “Everything’s combined there,” Piacentini said, “and that’s why it has the biodiversity [that it does].”
However, South America’s rich biodiversity faces significant threats. Deforestation, mercury mining, and climate change pose increasing risks to its animal populations. Despite these challenges, there is still hope for mitigating the damage.
“We will certainly lose a lot of species,” Piacentini noted, “but every effort that we make to reduce our impact will save us a lot as well.”
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