The value of the global environment to human well-being, health and livelihoods fell by around 21.5 trillion AU dollars (20 trillion U.S. dollars) a year between 1997 and 2011 due to loss of wetlands, coral reefs and tropical forests, according to a latest research statement from the Australian National University (ANU) on Thursday.

The research report was written by scientists and economists from the ANU, Wageningen University in The Netherlands, the University of Denver in the United States, the University of South Australia, the University of Pittsburgh in the United States and the University of East Anglia in Britain.

According to the research, global ecosystem services measure the value of ecological systems to human well-being, on top of the usual economic measures contained in gross domestic product (GDP) figures.

The study, published in Global Environmental Change, found the total value of global ecosystem services in 2011 was 134 trillion AU dollars (124.8 trillion U.S. dollars) a year, down from 145 trillion U.S. dollars a year in 1997. That compares to global GDP of just 75.2 trillion U.S. dollars in 2011.

"Nature is not just a pretty place. Nature is a large and important part of the real economy which adds to human well-being," said lead author Professor Robert Costanza, from ANU's Crawford School of Public Policy.

According to the statement, the report is the first time scientists and economists have put a dollar value on the loss of global ecosystem services, highlighting the need for policymakers to take a closer look at issues affecting environmental change.

"It allows us to build a more comprehensive and balanced picture of the assets that support human well-being and human's interdependence with the well-being of all life on the planet," Professor Costanza said.

And he said Australia's ecosystem services were estimated to be worth around 5.4 trillion AU dollars (5 trillion U.S. dollars) a year, compared to GDP of around 1.5 trillion U.S. dollars. And the drop in the global value was partly due to the loss of tropical forests and wetlands around the world and loss of coral reefs.

In addition, the report found the global area of tropical forest had declined by 642 million hectares between 1997 and 2011, while deserts had grown by 234 million hectares.

It also found coral reefs have gradually been turned into seagrass and algae beds. The area of ocean coral has shrunk by 34 million hectares, while seagrass and algae beds had grown by the same amount between 1997 and 2011.

And it found the global area of wetlands has shrunk by 14 million hectares.

"We are losing wetlands as they are converted into farmlands, urban and other uses," Professor Costanza said.(Xinhua)