Cape Town is the most biologically diverse city in the world, according to the City Nature Challenge; and it’s all thanks to citizens who heeded the global call to record plant and animal species in their cities.
The City Nature Challenge is an initiative started in the United States in 2016 with the aim of documenting biodiversity in Los Angeles and San Francisco. It became a global event in 2018.
The 2019 edition is the first that Cape Town has participated in. The city beat 59 others with 53,763 observations by 1,141 people who recorded 4,588 different species.
Cape Town was followed by La Paz, Bolivia, which had 46,931 observations and 3,006 species recorded by 1,500 people. These were followed by San Diego County, in the US; San Francisco; and Tena, in Ecuador.
Tony Rebelo, a senior scientist at the South African National Biodiversity Institute (SANBI) said: “We did not just win the challenge. We totally outperformed all other cities when it came to species.”
The challenge is open to any citizen and all they need to do to participate, according to citynaturechallenge.org, is “find wildlife… It can be any plant, animal, or any other evidence of life found in your city."
Once they’ve found the wildlife, people then photograph it and share it on iNaturalist and their city’s chosen platform.
According to citynaturechallenge.org, the ultimate goal of the challenge is to make people “become aware that biodiversity exists and matters, not only in the wild but also in cities.”
Besides being the most biologically diverse city in the world, Cape Town also boasts the honour of being home to the highest number of unique species found nowhere else on Earth.
“Incredibly it has the highest known concentration of plant species in the world. Its nearest rival, the South American rainforest, has only one third the number of species,” Conservation South Africa explains on their website.
“Even more remarkable is that 70% of the Cape’s impressive 9,600 plant species grow nowhere else on Earth,” it adds.
But even so, the city’s unique flora is slowly dying out.
A study published in the Nature Ecology and Evolution journal in June found that 37 plant species have become extinct since 1900. Hawaii lost the highest number of plants with 79, while Mauritius lost 32.
“And again, Cape Town is outperforming all other cities on earth,” says Rebelo. “If the Cape Flora is the second worst place on earth for species threatened with extinction, the Mother City is the city with the largest problem.”
He added: “Cape Town has a huge responsibility for conservation of our biodiversity.”