Surprising plant survivors in Three Gorges Dam 'death zone'

Five years ago, as a team from the Wuhan Botanical Garden embarked on a study of environmental impacts of the massive Three Gorges Dam, they made a startling discovery - almost 40 species of mostly common trees and plants could survive many metres underwater for more than half a year.

The dam, one of the largest in the world, has three main purposes: navigation, power generation and controlling a waterway responsible for some of the most catastrophic floods encountered.

To do this, the dam was envisaged as conquering nature. In reality, its "anti-seasonal" engineering has reversed it - keeping water levels high in the dry of winter, and much lower in the summer when the worst floods occur.

As a result, water levels along the Yangtze River above and below the dam can fluctuate by up to 30 metres, from a high of 175 metres above sea level in winter, to 145 metres in summer.

The initial government-funded study was to examine the effects and, if needed, remediation of what Dr Yang Fan described as a 40,000 hectare "death zone" for plants in the 30 metres between high and low water.

However, the team found that in the space of a decade or so - a short period in evolutionary terms - the plants have developed a range of effective survival strategies to cope with sudden, severe changes of environment, such as going from being "on land" to dwelling on the bottom of a lake.

In the past, plants along the river only had to deal with brief flooding in summer, but now they "suffer serial submergence stress [for] as long as 210 days at depths of up to 30 metres," Fan wrote in a paper published in the online peer-reviewed journal PlosOne in September. "Few plant species can tolerate such submergence stress."