Cities Drive Plants Extinct

"If we want to keep plant diversity in our cities, we need to protect and restore areas of native vegetation," says Dr Hahs. "Plants and people can coexist in urban areas. We just need to consider vegetation as a long-term investment rather than as a disposable asset."

Both the pace of urban change and how many plants remain in a city are good predictors of whether plant species will survive there in the future, says a recent report.

"The rapid and ongoing growth of cities and towns significantly threatens global biodiversity," says Dr Amy Hahs, a scientist working at the Australian Research Centre for Urban Ecology at the Royal Botanic Gardens in Melbourne, Australia. The team compiled raw data on plant extinctions within 22 urban areas, organized into three categories.

First, they examined cities in which the native flora started to be transformed more than 400 years ago. Almost all are European cities, including Glasgow in the UK, Vienna in Austria, and Zurich in Switzerland. Hong Kong is also included as it experienced extensive landscape transformation prior to 1600AD, before urbanization.

They also categorized cities in which the native flora started to be transformed after 1600 AD, but before any floral surveys could be completed. Such cities include New York City and Chicago in the US and Auckland, New Zealand and Singapore.

The third category included cities that had large areas of native flora at the time they were surveyed, but subsequently were transformed by urban development. Los Angeles and San Diego in the US, Melbourne and Adelaide in Australia, Capetown and Durban in South Africa were included here. Cities belonging to the first two categories had by far the highest extinction rates.

"Under current planning and design practices, it is very hard to maintain 30 percent native vegetation within an urban area, but finding ways around this problem either through innovative design or restoration will help preserve local biodiversity," says Dr Hahs.