单选题 A third of the planet's land is severely degraded and fertile soil is being lost at the rate of 24bn tonnes a year，according to a new United Nations-backed study that calls for a shift away from destructively intensive agriculture.The alarming 26_____ ，which is forecast to continue as demand for food and productive land increases，will add to the risks of conflicts unless 27_____ actions are implemented，warns the institution behind the report.

"As the ready supply of healthy and productive land dries up and the population grows，competition is 28_____ for land within countries and globally," said executive secretary of the UN Convention to Combat Desertification (UNCCD) at the .launch of the Global Land Outlook."To 29_____ the losses，the Outlook suggests it is in all our interests to step back and rethink how we are managing the pressures and the competition."

The Global Land Outlook is 30_____ as the most comprehensive study of its type，mapping the interlinked impacts of urbanization，climate change，erosion and forest loss.But the biggest factor is the 31_____ of industrial farming.Heavy tilling，multiple harvests and 32_____ use of agrochemicals have increased yields at the 33_____ of long-term sustainability.In the past 20 years，agricultural production has increased threefold and the amount of irrigated land has doubled，notes a paper in the Outlook by the Joint Research Centre (JRC) of the European commission.Over time，however，this 34_____ fertility and can lead to abandonment of land and 35_____ desertification.

空白处35.应填无