Chile in the 1970s planted millions of Monterey pine and eucalyptus trees for timber, but scientists now say many native forests have been replaced, while streams and wildlife have declined

Half a century of satellite images has just revealed something startling. A stretch of coast in central Chile that scientists consider a global biodiversity hotspot has seen a massive loss of native forest since 1960, and the reason is pine trees.

According to the study ‘Pine plantations and five decades of land use change in central Chile,’ by researchers from the University of Chile and the University of Wisconsin-Madison and published in PLOS ONE, the transformation began earlier than most people think. The team combined aerial photographs from the 1950s and 60s with satellite images from 1975, 1998, and 2014, verifying more than a thousand sample points across about 950,000 hectares of Chile’s Coastal Range, an area comparable in size to Rhode Island and Delaware combined. What they found: by 1960, pine plantations already occupied 12 percent of that land, by 1975 they had risen to 18 percent, then shot up to 38 percent by 1998, before finally levelling off at 37 percent by 2014.

The study’s point-by-point land-cover analysis used a 3-km systematic grid and 1,039 sample points to classify change over six decades. It found native forest cover fell from 60% of the region in 1960 to 18% by 2014, while pine plantations expanded from 14% to 42%, with most of the shift occurring after 1975.


Why pine won out over forest and farmland
The driving force was economic, not accidental. Monterey pine, the species planted almost everywhere in the study, grows fast and produces high-quality wood, making it enticing to Chile's timber and pulp industry. The same PLOS ONE study says government policy also helped. Chile’s first forest law, passed in 1931, provided tax exemptions to landowners who planted trees on land damaged by more than a century of wheat farming, and a second law, Decree 701, passed in 1974, broadly extended subsidies for reforestation.

The paper notes that these incentives hit landowners at exactly the moment Chile’s forestry sector was industrializing, so plantations could spread quickly across degraded land. In the study area, pine cover rose from 18% of sample points in 1975 to 38% in 1998, while native forest dropped from 54% to 28% over the same period.

The steepest losses took place between 1975 and 1998. During that time, native forest was lost at a rate of 1.74 percent a year. Researchers found that by 1998, 40 percent of all the forests standing in 1975 had been replaced by pine plantations. Agricultural and livestock land also fell, but more slowly, with annual rates of decline of 0.62 percent, 0.92 percent, and 0.95 percent over the three periods studied.

There was also the copycat effect. The study also found that forests adjacent to existing pine plantations were much more likely to be cleared and replanted, a pattern researchers describe as contagious because landowners watching their neighbors profit from pine tended to follow suit.

Streams are running drier under the plantation cover
The forest swap has not been confined to the trees themselves. A peer-reviewed study, ‘The Impacts of Native Forests and Forest Plantations on Water Supply in Chile,’ published in the journal Forests and analyzing 25 large forested catchments in south-central Chile, found that annual runoff decreases with increasing forest plantation area by around 2.2 to 7.2 percent for every additional 10,000 hectares planted. Fast-growing pine and eucalyptus just suck more water out of the soil than native forest or grassland does, leaving less to flow downstream, a trend that has caused real concern in Chilean farming communities that rely on those same streams during the country’s dry summers.

According to the authors, the runoff response was strongest in catchments where plantations covered a larger share of the basin, and the effect persisted even after accounting for climate and topography. They also found native forest cover was positively associated with water yield, making the replacement of forests with pine and eucalyptus a direct hydrological trade-off.

What this means for wildlife
Native forest and pine plantation are not equivalent habitats. While agricultural land converted to pine plantations can benefit some forest wildlife once the trees mature and are well managed, plantations still lack many of the structural features that native forests provide, such as diverse understory plants, dead wood, and varied tree ages, says the PLOS ONE researchers. To prevent further species loss in the future, the study authors conclude that native forest recovery and habitat restoration are needed in the region.

The paper warns that some forest birds and plants can persist in plantations only when stands are mature and structurally complex, but those communities remain less diverse than in native forests. The authors therefore argue for protecting remaining native patches, restoring degraded areas, and limiting further plantation expansion into forested land.

It's not just Chile's problem
This local story is part of a much bigger global pattern. In the study, ‘High-Resolution Global Maps of 21st-Century Forest Cover Change,’ published in Science, Matthew Hansen and colleagues at the University of Maryland reported that the world lost 2.3 million square kilometers of forest between 2000 and 2012 and gained only 0.8 million square kilometers across the globe, with the tropics and subtropics suffering the steepest losses and fastest turnover from intensive forestry. That study is a reminder that forest cover numbers on a map can look stable, or even improve, while the actual ecosystem underneath keeps changing hands from native woodland to commercial plantation.

A separate, earlier study of a nearby stretch of the same Chilean coastal region backs this up with even sharper numbers. According to a study by Cristián Echeverría and colleagues published in Biological Conservation, the pace of deforestation was about 4.5 percent per year, meaning that native forest cover in that area shrank by 67 percent between 1975 and 2000, one of the fastest rates recorded anywhere in the world at that time.
Is the story turning a corner?
There is a small silver lining, but it comes with a price. By 2014, pine plantation coverage had actually fallen back a little, not because native forest was recovering, but because a chunk of that pine acreage was being converted again, this time into eucalyptus, which grows even faster and feeds Chile's paper industry. The PLOS ONE study showed that in 2014, eucalyptus stands accounted for about 18% of pine plantations from 1998.

But there is reason for cautious optimism going forward, researchers say. Larger timber companies are increasingly required to protect remaining native forest patches within their land holdings to meet international certification standards associated with the wood and paper they export. But the researchers say the system largely applies to big exporters, leaving small landowners largely out of the loop.

Why this matters beyond Chile
For American readers, the connection is not abstract. US consumers buy Chilean wood pulp, paper, and fruit grown on land that used to be forest. Chile’s plantation model is based on the same basic trade-off that supports many rural US timber regions: fast-growing trees on marginal land replacing lost farm income. The Chilean experience is a natural experiment in what happens when that trade-off is left largely unchecked for fifty years. The study authors say that once the native forest disappears, the study's authors note, replanting pine or eucalyptus doesn't restore the same wildlife habitat or ecosystem functions, even though the land still counts as "forest" on paper.