Forest cover around the world will continue a slow shrinking before stabilizing at a lower level, according to a new study from the University of Guelph. Researchers analyzed forest trends from around the world and developed a mathematical model to show future land use changes.

They found the most likely model shows forests will decline from 30 per cent of Earth's land mass today to 22 per cent within the next two centuries. The model discusses different scenarios, such as global forest growth reversing deforestation, or reforestation cut short by renewed losses.

"Outlook on a worldwide forest transition" appears in the October 9, 2013 issue of PLOS ONE, was written by Chris Pagnutti, an NSERC post-doctoral researcher in the School of Environmental Sciences (SES) and Department of Mathematics and professors Chris Bauch, Mathematics and Statistics, and Madhur Anand, SES and University Research Chair in Sustainability Science.

They analyzed several centuries' worth of forestry data from the Food and Agricultural Organization of the United Nations and other sources in the literature. Perhaps surprisingly, forest cover has held steady and even grown slightly in industrialized nations. In developing countries, forests are declining as populations grow and farming claims more land. Worldwide since 1990, forests have declined by more than 70 million hectares, a land mass greater than France.

"This model is helpful in that we can look back at where we've come from, but its real usefulness is in predicting where we're most likely heading," said Anand.

"With growing international trade in forest products playing a role, it is more informative to look globally at forest cover than it is to do a nation-by-nation analysis."

They used the world food equation, which relates agricultural land area to population, per capita consumption and farm yield. The model quantifies how much farming improvements, such as increased yield, reduce the amount of land needed to feed a growing population.

But if world population reaches 10 billion (based on mathematical trends), human uses will take up about two-thirds of the world's land area. With 15 per cent of Earth's land mass already classified as arid, only 22 per cent would be left for forest and wild pasture conservation.

"We tried to keep this model simple so there aren't too many unknown parameters. We realize that no one can determine the future, and there could be drastic changes in agricultural yield, food technologies or diet which could impact on our findings, but we attempted to explore those kinds of changes in our scenarios," said Anand.

"Based on this model, we are most likely going to see forest cover decline around the world. Countries need to realize that this is a global issue, and if forests are to be preserved, and even grow, co-operation through intergovernmental organizations will have to continue to happen.

"Industrial countries could, for example, disseminate technologies to developing countries, reducing the amount of land needed for agriculture. Otherwise, we will see forests get smaller and smaller."