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Trade and climate change increase pest threat to Europe’s forests

By | Climate change, News, Plant Health

Europe’s forests face a growing threat from pests due to global trade and climate change, but scientists are developing techniques that can give an early warning of infestations to help combat damaging insects and diseases.

Pests are responsible for damaging 35 million hectares of forest around the world every year. In the Mediterranean region alone an area the size of Slovakia – five million hectares – is affected by pests annually, according to the UN Food and Agriculture Organization (FAO).

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 more widely.

Only a tiny proportion of exotic pests that arrive in Europe end up damaging trees. ‘But these are very harmful, and there are more and more (of them),’ said Dr Hervé Jactel, director of research for forest entomology and biodiversity at the French National Research Institute for Agriculture, Food and Environment

On average, six new species of tree pests are being introduced to Europe every year, up from two a year in the 1950s, says Dr Jactel. They arrive in potted plants and wooden products or packaging.

Many of the emerging threats to Europe’s forests originate in 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. It is now knocking at Europe’s door.

‘We know it will kill all ash trees, or most of them,’ said Dr Jactel, who is the coordinator of the HOMED project which is developing new ways to detect such exotic pests early.

The polyphagous shot-hole 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 issue for Europe.’

This little insect originated in Asia, spread to Israel, California, and then South Africa where it has killed hundreds of thousands of trees. In April this year it was discovered for the first time in Italy, in a tropical garden. There is no sign yet that it has spread anywhere else in Europe.

Despite all of the countries affected by the beetle being on the alert for it, none were able to detect it until it had already caused damage, says Dr Jactel. The problem is spotting exotic pests and pathogens before they start attacking trees.

Hundreds of thousands of containers filled with goods arrive in Europe’s harbours and airports every day. Tiny insects or spores from fungal diseases can stow away in shipments containing wooden products, pallets or packaging, or live plants. The sheer number of shipments is overwhelming the resources of sanitary inspectors to detect insects and spores, says Dr Jactel.

‘It’s like finding a needle in a haystack.’


Once the containers are opened, pests can then easily escape to nearby trees. So increasing surveillance of 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 growing. The forestry sector accounts for approximately 1% of EU GDP, and provides jobs for some 2.6 million people. If allowed to run rampant – without the natural predators found in their native habitats and among trees that have not evolved defences 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 are developing generic traps to attract a wide variety of insects. These will be placed in shipping containers before they set off from their country of origin, and in airports, harbours and train stations where the imports arrive.

The teams are also developing traps for fungal spores, and DNA tools and databases of species to help identify whether a spore is local or imported.

The project is also planting ‘sentinel’ European trees in Asia, North America and elsewhere that can help scientists identify early which pests might pose a particular threat to European trees.

For pests that have already taken hold in Europe, one possible solution is to import that pest’s natural enemies from its country of origin, says Dr Jactel.

Scientists in France and Switzerland are investigating whether the natural enemies of the destructive box tree moth – which has spread from China across Europe –  can be imported and used to contain it. But releasing this parasitic wasp to target the moths might bring other problems.

‘We need to be very cautious to check the Chinese parasitoids won’t affect European species,’ said Dr Jactel.

Native pests

Many threats to Europe’s forests, however, are closer to home. A warming climate in many regions is helping some native pests to become more common.

The bark beetle is one of the most damaging pests currently attacking Europe’s forests, destroying spruce trees in Central Europe.

The Czech Republic has had to cull so many infected trees in recent years the price of wood has plummeted as the resulting timber has been sold off, says Dr Julia Yagüe, project manager of My Sustainable Forest (MSF), which monitors the health of Europe’s forests. Spruce trees take up to 140 years to fully grow, so the loss of so many trees will be felt for a long time.

This is largely because warming temperatures have allowed the beetles to breed more frequently.

‘Some 20 years ago, we’d have one breeding cycle per summer, but nowadays we have up to four breeding cycles of bark beetle in the Czech Republic and southern Germany,’ said Dr Yagüe.

Warmer, longer and drier summers also mean trees are more vulnerable to attack because the conditions leave them less able to cope with pests, she says.

Scientists are creating variations of native spruce trees, which they hope will be more resistant to higher temperatures and drought, and so better able to fight off attacks from pests.

But in the meantime, forests urgently need closer monitoring, says Dr Yagüe. Forest managers usually take an inventory once every five to ten years. 

‘Because climate change is pressuring so hard, we need to update our data on forests much more often,’ she said.

The most efficient way to monitor large forests is with satellite observations, which can help detect the early warning signs of trees that are under water or heat stress, and so are more susceptible to attack.

They can also allow forest managers to spot the first signs of an infestation, such as dryness, loss of foliage, or dieback.

‘With remote sensing from satellites we can spot this sickness before even the human eye can detect it,’ said Dr Yagüe, who is a remote sensing expert at the Spanish aerospace company GMV.

MSF’s job of gathering data became easier with the launch of Europe’s Copernicus satellites in 2014, and the development of technology able to process huge amounts of information.

MSF now receives snapshots of Europe’s forests every five days instead of every 15 to 30 days before Copernicus. ‘We get this information for free,’ said Dr Yagüe.

But there is another crucial element to improving the health of Europe’s forests which is much closer to home.  

Many of Europe’s forests have been abandoned. While they were once carefully managed landscapes, as people moved to cities, ‘the knowledge of living together with nature has been lost’, said Dr Yagüe. ‘Recovering this is super important.’

The research in this article was funded by the EU.

Article source: Horizon Magazine

Author: Alex Whiting

Image: The emerald ash borer has killed more than 150 million trees in the US in the last decade and is a potential threat to Europe’s forests. Credit: Pikist, public domain

Research: Crop Plants Are Taking Up Microplastics

By | News, Plant Science

Microplastics, tiny plastic particles less than 5 millimeters in length, can now be found throughout the ocean and other aquatic ecosystems, and even in our seafood and salt. As microplastics have become ubiquitous, scientists have become concerned about their transfer from the environment to the food chain and their potential impact on human health.

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Scientists Reconstruct Spring Hydroclimate on South-central Tibetan Plateau by Living and Dead Alpine Juniper Shrubs

By | Climate change, Forestry, News, Plant Science

Alpine regions on the Tibetan Plateau are sensitive to climate change, however, little is known about their long-term hydroclimate variability due to short instrumental records. A research team established a 537-year standard shrub-ring chronology by cross-dating living and dead Wilson juniper shrubs sampled nearby the Nam Co Lake, on the south-central Tibetan Plateau.

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Making sense of climate scenarios: toolkit for decision-makers launched

By | Agriculture, Climate change, News

To make climate scenarios work for decision-makers, an international team of researchers developed a comprehensive interactive online platform. It is the first of its kind to provide the tools to use those scenarios – from climate impacts to mitigation and energy options – to a broader public beyond science. The scenarios help policy makers and businesses, finance actors and civil society alike to assess the threat of global warming and ways to limit it.

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First potentially invasive species to reach the Antarctica on drifting marine algae identified

By | Climate change, News, Plant Science

Drifting algae in the Austral Ocean can bring invasive species to the Antarctic coasts, according to a new study. The report describes the first scientific evidence of a potentially invasive and colonial species –the marine bryozoan Membranipora membranacea- which reaches the Antarctic latitude islands in macroalgae that drift in the marine environment.

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Lotus japonicus

Plant genomes reveal the basis for adaptation to contrasting climates

By | News, Plant Science

In the face of rapid climate change, it is important that plants can adapt quickly to new conditions to ensure their survival. Using field experiments and plant genome studies, an international research team has pinpointed areas of the genome that are affected during local adaptation to contrasting climates. This new insight into local adaptation represents an important first step towards future development of crops that are resilient to climate change.

It is an open question how we can ensure that our crop plants remain productive in a changing climate. Plants are confronted with similar climate adaptation challenges when colonising new regions, as climate conditions can change quickly across latitudes and landscapes. Despite the relevance of the question, there is very limited basic scientific insight into how plants tackle this challenge and adapt to local climate conditions. Researchers from Denmark, Japan, Austria and Germany have now published the results of their research on this very subject.

The researchers studied the plant Lotus japonicus, which – with relatively limited genomic changes – has been able to adapt to diverse Japanese climates ranging from subtropical to temperate. Using a combination of field experiments and genome sequencing, the researchers were able to infer the colonisation history of L. japonicus in Japan and identify areas in the genome where plant populations adapted to warm and cold climates, respectively, showed extreme genetic differentiation. At the same time, they showed that some of these genomic regions were strongly associated with plant winter survival and flowering.

This is the first time researchers have identified specific genomic regions that have changed in response to natural selection to allow the plant species to adapt to new climatic conditions.

Professor Mikkel Heide Schierup states: “One of the great questions of evolutionary biology is how natural selection can lead to genetic adaptation to new environments, and here we directly observed an example of this in Lotus japonicus.”

And Associate Professor Stig Uggerhøj Andersen adds:  “Yes, and it is fascinating that we have identified specific traits, including winter survival, that have been under selection during plant local adaptation to contrasting climates. At the same time, we observed extreme genetic signatures of selection in specific genomic regions. This link between selection signatures and specific traits is critical for understanding the process of local adaptation.”

“The rapid adaptation of L. japonicus to widely different climates indicates that genetic variation underlying the adaptations was already present before plant colonisation. This is promising for other plant species on a planet with rapid climate change, since it will allow more rapid adaptation,” adds Professor Schierup.

“In this case, the different climates have resulted in distinct plant populations adapted to their own local environments. These populations appear to be preserved because certain genotypes are an advantage in warm climates, but a disadvantage in cold climates and vice versa,” concludes Dr. Andersen.

Read the paper: Nature Communications

Article source: Aarhus University


Image credit: Niels Sandal, Aarhus University