Pests are responsible for damaging 35 million hectares of forest worldwide each year .
According to the Food and Agriculture Organization of the United Nations (FAO), only the Mediterranean region, with an area the size of Slovakia (five million hectares), is affected by pests each year.
And the threat posed by insects and pathogens appears to be growing. Climate change is allowing some native pests to breed more frequently , while international trade is spreading exotic insects and pathogens widely .
Only a small proportion of the exotic pests that reach Europe end up damaging the trees. “But these are very harmful, and there are more and more,” said Dr. Hervé Jactel, research director for forest entomology and biodiversity at France’s National Research Institute for Agriculture, Food and the Environment.
On average, six new species of tree pests are introduced to Europe each year , compared to two that were introduced annually in the 1950s, says Dr. Jactel. They arrive in pots and in wooden products or in containers. Many of the new threats to European forests originate from Asia.
The emerald ash borer , for example, spread from Asia to the United States, where it killed more than 150 million trees and may have cost more than $ 10 billion in the last decade. Now he is knocking at the door of Europe.
“We know it will kill all or most ash trees,” said Dr. Jactel, coordinator of the HOMED project, which is developing new ways to detect such exotic pests early.
The polyphagous borer is another major threat. It can attack virtually all deciduous tree species in Europe, says Dr. Jactel. “It’s a very, very dangerous tiny beetle,” he said. “This is probably the next big problem for Europe.”
This tiny insect originated in Asia, spread to Israel, California, and then South Africa, where it has killed hundreds of thousands of trees. In April of this year it was discovered for the first time in Italy, in a tropical garden. There are no signs yet that it has spread anywhere else in Europe.
Although all the countries affected by the beetle are on alert for it, none were able to detect it until it had already caused damage, says Dr. Jactel. The problem is detecting exotic pests and pathogens before they start attacking the trees.
Hundreds of thousands of containers full of goods arrive at Europe’s ports and airports every day. Small insects or fungal disease spores can hide in shipments containing wood products , pallets, packaging, or live plants. The large number of shipments is straining the resources of sanitary inspectors to detect insects and spores, says Dr. Jactel. “It’s like finding a needle in a haystack.”
Solutions
Once the containers are opened, pests can easily escape to nearby trees. So increasing surveillance of the trees growing around ports and airports is a good starting point, says Dr. Jactel.
Finding solutions to these pests is vital. Forests cover 43% of the EU’s land area (182 million hectares in total) and continue to grow. The forestry sector accounts for around 1% of the EU’s GDP, and provides employment for some 2.6 million people. If allowed to overflow (without the natural predators found in their native habitats and among the trees that have not developed defenses against them), the pests could be devastating.
But new tools are also needed to alert inspectors to the presence of pests in containers before they can escape, he adds.
The HOMED team is developing generic traps to attract a wide variety of insects . These will be placed in the shipping containers before they leave their country of origin and at the airports, ports and train stations where imports arrive.
The teams are also developing fungal spore traps and DNA tools and species databases to help identify whether a spore is local or imported.
The project is also planting European “sentinel” trees in Asia, North America and elsewhere, which can help scientists identify pests early on that could pose a particular threat to European trees.
For pests that have already taken root in Europe, a possible solution is to import the natural enemies of that pest from their home country , says Dr. Jactel. Scientists in France and Switzerland are investigating whether natural enemies of the destructive boxwood moth, which has spread from China throughout Europe, can be imported and used to contain it. But releasing this parasitic wasp to attack moths could bring other problems. “We must be very cautious to see that Chinese parasitoids will not affect European species,” said Dr. Jactel.
Native pests
However, many of the threats to Europe’s forests are closer to home. Warming climates in many regions are helping some native pests to become more common.
The bark beetle is one of the most damaging pests currently attacking Europe’s forests , destroying fir trees in Central Europe.
The Czech Republic has had to cull so many infected trees in recent years that the price of wood has plummeted, as the resulting wood has been sold, says Dr. Julia Yagüe, project director of My Sustainable Forest (MSF ), which monitors the health of Europe’s forests. Fir trees take up to 140 years to fully grow, so the loss of so many trees will be noticeable for a long time.
This is largely because warming temperatures have allowed the beetles to reproduce more frequently. “About 20 years ago, we had one breeding cycle in summer, but today we have up to four breeding cycles for bark beetles in the Czech Republic and southern Germany,” Yagüe said.
Warmer, longer and drier summers also mean trees are more vulnerable to attack because conditions leave them less able to cope with pests, he says.
Scientists are creating variations of native fir trees, which they hope will be more resistant to higher temperatures and drought, and therefore better able to combat pest attacks.
Meanwhile, forests urgently need closer monitoring, says Dr. Yagüe. Forest managers usually do an inventory every five to ten years. “Because climate change is pushing so hard, we need to update our forest data much more frequently,” he said.
The most efficient way to monitor large forests is with satellite observations , which can help detect the first warning signs of trees that are under water or thermal stress, and therefore more susceptible to attack. They can also allow forest managers to detect the first signs of an infestation, such as dryness, loss of foliage, or death. “With remote sensing from satellites we can detect this disease even before the human eye can detect it,” said Dr. Yagüe, who is an expert in remote sensing at the Spanish aerospace company GMV.
MSF’s work on data collection was facilitated with the launch of the European Copernicus satellites in 2014, and the development of technology capable of processing large amounts of information.
MSF now receives snapshots of European forests every five days instead of every 15 to 30 days before Copernicus. “We receive this information for free,” Dr. Yagüe said.
But there is another crucial element for improving the health of European forests that is much closer to home. Many of Europe’s forests have been abandoned . While they were once carefully managed landscapes, when people moved to cities “the knowledge of living with nature lost,” Dr. Yagüe said. “Getting this back is super important.”
Artículo original
This article was originally published in Horizon, the EU Research and Innovation Magazine
