Weeds and Rainforest: Breaking a Vicious Cycle of Deforestation

A new study has revealed the complexities of deforestation, showing that a very wasteful land management strategy is not only encouraging the decline of our world's rainforests, but actually making little use of the resulting cleared land. Now experts are suggesting a new strategy.

According to the most recent data on deforestation, we lose well over 80,000 square miles (130,000 km²) of rainforest to agricultural land clearing and logging each year. That's an area equivalent to the size of Greece. Stunningly, the majority of this clearing is to make room for new pastures where cattle and other livestock can graze.

And while the simple idea of clearing entire age-old ecosystems just so a handful of cows can munch on grass may seem absurd, what's even more startling is that these cleared pastures are only used for three to four years before they are utterly abandoned.

That's because livestock fields in regions like Ecuador quickly become overrun with particularly stubborn weeds that are all but completely immune to common herbicides and even burning. Soon after weeds like bracken move in to hedge out cow-feed, farmers have to move on and start clearing new areas of forest.

"This cycle has to be broken," researcher Thomas Knoke, from the Institute of Forest Management at Technische Universität München (TUM), said in a statement. "We've been investigating whether this abandoned pasture land can be recultivated, and if so, how." (Scroll to read on...)

According to a study recently published in the journal Nature Communications, Knoke and his colleagues used a swath of cleared land in the Ecuadorian Andes to test a number of strategies that could put these abandoned lands back into use.

They tested the benefits of five different strategies: leaving the land to nature, using the land to grow alder trees, using the land to grow non-native pines, using expensive mechanical weed control, or attempting intensive chemical weed control and soil fertilization.

Not surprisingly, the researchers found that re-introducing alder trees was both very possible and particularly sustainable, putting this abandoned land to the best use.

"Our study also showed that afforestation with the native Andean alder had a much more positive impact on the climate and water balance than the other land use options," added researcher Jörg Bendix.

However, the team is quick to admit that this isn't a perfect solution. They found that if farmers were to start growing alders on abandoned land for profit, as opposed to their current slash-and-burn policy, they would feel some notable losses in earnings. To get these farmers to cooperate, the researchers believe compensation from the government or some other incentive would be necessary.

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