Scientists have identified and named more than a million animal species, and there are millions more yet to be discovered on Earth’s seven continents. But which continent has the most animal species?
For hundreds of years, scientists have been cataloging and geolocating species around the world. Before the digital age, most of our information about species distributions came from museum collections Victor Piacentinian ornithologist at the Federal University of Mato Grosso in Brazil. Today, the public also contributes to this effort.
Over the past 20 years, there has been a “revolution” in citizen science, Piacentini told Live Science, and “scientists are using their data to fill in the gaps.”
Using this information, scientists can map the distribution of species worldwide. In the late 1980s, scientist Norman Myers coined the term ‘biodiversity hotspot“to refer to places with an exceptionally high number of species for their area. From the now 36 hotspots Worldwide, most are located on continents that straddle the equator, where the climate is warm and humid.
The reason for this not only has to do with animals, but also with plants. “Plants are the basis of species,” Barnabas Daruan applied ecologist at Stanford University, told Live Science. “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.”
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Although plants can live in a variety of conditions, most thrive in warm, moist places. The humidity and heat work together to provide essential moisture: warm air traps water molecules to create humidity. Heat is also better for many microorganisms, especially decomposers, which break down dead material that plants harvest for nutrients.
In addition, insects, which pollinate many flowering plants, are better suited to warmer climates because they cannot regulate their own body temperature. Having more insects in the tropics means more pollination for plants and more food for hungry predators, Daru said.
But Piancentini noted that other factors are also at play. To accommodate many species, a continent must provide not only tropical conditions but also a variety of habitats. Places with high biodiversity have many potential niches for animals to occupy, Piacentini said. For example, tall trees or tall mountains create vertical variation in temperature, sun exposure and terrain, allowing more critters to coexist without competing for the same resources or habitat.
Based on these factors and estimates from museum and citizen science data, most scientists agree that South America has the highest number of animal species. From the Amazon rainforest, which has four tree layers for animals to live in, to the Andes Mountains with dozens of different microclimates, South America has a winning mix of heat and geography. “Everything is combined there,” Piancentini said, “and that’s why it has the biodiversity [that it does].”
That said, South America’s biodiversity may not always be as vibrant as it is today. With deforestationmercury mining and climate changeSouth America’s animals face more threats than ever before. However, there is still an opportunity to limit the damage.
“We will certainly lose many species,” Piacentini said, “but any effort we make to reduce our impact will also save us a lot.”