Southeast Europe swelters through another heatwave with a human fingerprint



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Searching for respite from the heat in one of Rome’s fountains.
Max Roxxi/Reuters

Andrew King, University of Melbourne

Parts of Europe are having a devastatingly hot summer. Already we’ve seen heat records topple in western Europe in June, and now a heatwave nicknamed “Lucifer” is bringing stifling conditions to areas of southern and eastern Europe.

Several countries are grappling with the effects of this extreme heat, which include wildfires and water restrictions.

Temperatures have soared past 40℃ in parts of Italy, Greece and the Balkans, with the extreme heat spreading north into the Czech Republic and southern Poland.

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Some areas are having their hottest temperatures since 2007 when severe heat also brought dangerous conditions to the southeast of the continent.

The heat is associated with a high pressure system over southeast Europe, while the jet stream guides weather systems over Britain and northern Europe. In 2007 this type of split weather pattern across Europe persisted for weeks, bringing heavy rains and flooding to England with scorching temperatures for Greece and the Balkans.

Europe is a very well-studied region for heatwaves. There are two main reasons for this: first, it has abundant weather observations and this allows us to evaluate our climate models and quantify the effects of climate change with a high degree of confidence. Second, many leading climate science groups are located in Europe and are funded primarily to improve understanding of climate change influences over the region.

The first study to link a specific extreme weather event to climate change examined the record hot European summer of 2003. Since then, multiple studies have assessed the role of human influences in European extreme weather. Broadly speaking, we expect hotter summers and more frequent and intense heatwaves in this part of the world.

We also know that climate change increased deaths in the 2003 heatwaves and that climate change-related deaths are projected to rise in the future.

Climate change’s role in this heatwave

To understand the role of climate change in the latest European heatwave, I looked at changes in the hottest summer days over southeast Europe – a region that incorporates Italy, Greece and the Balkans.

I calculated the frequency of extremely hot summer days in a set of climate model simulations, under four different scenarios: a natural world without human influences, the world of today (with about 1℃ of global warming), a 1.5℃ global warming world, and a 2℃ warmer world. I chose the 1.5℃ and 2℃ benchmarks because they correspond to the targets described in the Paris Agreement.

As the heatwave is ongoing, we don’t yet know exactly how much hotter than average this event will turn out to be. To account for this uncertainty I used multiple thresholds based on historically very hot summer days. These thresholds correspond to an historical 1-in-10-year hottest day, a 1-in-20-year hottest day, and a new record for the region exceeding the observed 2007 value.

While we don’t know exactly where the 2017 event will end up, we do know that it will exceed the 1-in-10 year threshold and it may well breach the higher thresholds too.

A clear human fingerprint

Whatever threshold I used, I found that climate change has greatly increased the likelihood of extremely hot summer days. The chance of extreme hot summer days, like this event, has increased by at least fourfold because of human-caused climate change.

Climate change is increasing the frequency of hot summer days in southeast Europe. Likelihoods of the hottest summer days exceeding the historical 1-in-10 year threshold, one-in-20 year threshold and the current record are shown for four scenarios: a natural world, the current world, a 1.5℃ world, and a 2℃ world. Best estimate likelihoods are shown with 90% confidence intervals in parentheses.
Author provided

My analysis shows that under natural conditions the kind of extreme heat we’re seeing over southeast Europe would be rare. In contrast, in the current world and possible future worlds at the Paris Agreement thresholds for global warming, heatwaves like this would not be particularly unusual at all.

There is also a benefit to limiting global warming to 1.5℃ rather than 2℃ as this reduces the relative frequency of these extreme heat events.

As this event comes to an end we know that Europe can expect more heatwaves like this one. We can, however, prevent such extreme heat from becoming the new normal by keeping global warming at or below the levels agreed upon in Paris.


The ConversationYou can find out more about the methods used here.

Andrew King, Climate Extremes Research Fellow, University of Melbourne

This article was originally published on The Conversation. Read the original article.

Europe’s oldest forest is threatened by a beetle infestation – let nature take its course


Lucinda Kirkpatrick, University of Stirling

Białowieza Forest is the kind of place you imagine from the Grimm fairy tales. Huge firs, oaks and ashes tower over you, woodpeckers and other birds call all around you and the guides who work there know the intimate history, and names, of many individual trees.

For anyone, it is a magical place – and, as a forest ecologist, visiting it was a dream come true. However, the features that make it so unique may be under threat thanks to new plans for large-scale logging.

Straddling the border between Poland and Belarus, Białowieza is the last remainder of the vast primeval forest that once covered most of Europe. It is a hotbed of biodiversity, home to nearly 20,000 plant and animal species including wolves, lynx and the largest remaining population of European bison. Rare birds, including several woodpecker species, provide a glimpse of the bird life that used to exist in European forests before humans transformed the continent.

The forest is home to around 800 bison.
Francesco Carrani, CC BY

Unfortunately, on the Polish side of the border, only one third of Białowieza Forest is protected. Outside of this area as much as 35% has been earmarked for felling and the fear is that this will result in an increasingly isolated small “island” of protected forest surrounded by fragmented and poorer quality woodland, which has already been shown to support lower bird populations than the protected park area.

Felling around Białowieza has been controlled in the past; quotas were set in 2012 to limit how much wood could be removed. However by 2015, 90% of that quota had already been logged – and the new proposals will triple the permitted volume of logging.

The proposal for further logging is controversial. Poland’s state forest department, Lasy Panstwowe, views the felling as necessary to combat outbreaks of spruce bark beetle, the larvae of which burrow under the bark of living spruce trees to lay its eggs. The developing larvae feed on inner woody layers and can eventually kill the tree.

Spruce bark beetles were here…and it didn’t end well for the tree.
Tõnu Pani, CC BY-SA

However, both local scientists and NGOs, such as Greenpeace Polska, argue that removing damaged trees will cause more harm than good and that further logging is driven by economic rather than management interests. Professor Tomasz Wesołowski, who has studied Białowieza’s birds for more than 30 years, told me it would be a disaster, as logging and replanting would completely change the quality of the forest habitat and threaten its UNESCO heritage site status. There is even a suggestion that this violates Poland’s environmental commitments under the EU’s Natura 2000 program.

The newly proposed logging areas cover 20% of the old-growth forest, as well as areas overgrown by endangered bog woodland habitat. Mass logging would dramatically alter the character of both the areas in question and the surrounding habitat – even more than the bark beetles.

In fact, across the world this form of “salvage logging” to recover economic value from damaged forests often causes more damage to ecosystems than the initial natural disturbance. After a bark beetle invasion hit Sumava National Park, that stretches across the border between Bavaria and the Czech Republic, evidence showed that salvage logging delayed forest recovery.

There’s life in dead wood

The proposed increased logging in Białowieza includes removing quantities of dead wood, yet this dead wood plays an important role in the functioning of a healthy forest. Forests are often built from the bottom up, with dead wood as the foundation.

While aesthetically they may not be that pleasing for us, dead trees are a vital habitat for saproxylic insects which feed on dead and decaying matter. Białowieza supports large populations of endangered saproxylic beetles and invertebrates which rely on dead wood and, in turn, these provide food for birds, small rodents such as shrews and voles, and bats including the rare barbastelle. In turn these animals are eaten by larger predators such as owls, wolves and lynx.

The forest food web starts here.
Aleksander Bolbot / shutterstock

Dead and dying spruce stumps are almost exclusively used by some woodpecker species as nests and also act as great hosts for lichens and mosses, some of which are facing extinction in Europe. If the dead wood is removed, the entire forest ecosystem will suffer.

Logging is unnecessary

Logging is not the only solution to the spruce bark beetle problem. Pheromone traps, for instance, effectively attract large numbers of beetles while outbreaks in the UK are controlled by unleashing a specific predator beetle, Rhizophagus grandis, that targets the spruce beetle. Due to its widespread use in commercial forestry, R. grandis is relatively cheap and readily available, and Forestry Commission research showed it was more effective at controlling outbreaks than salvage logging.

In any case, a beetle infestation might be disastrous for individual trees but it won’t necessarily harm the forest itself. Like many ecosystems, Białowieza is vulnerable to climate change. As species such as Norway spruce are weakened by changing climatic conditions, the bark beetle is able to take hold. This is an invaluable part of the forest regeneration process, allowing deciduous trees that are better able to cope with changing climatic conditions to grow in the gaps left by dying spruces. In the long run it may be better for Białowieza Forest to let nature, and regeneration, take its course.

The Conversation

Lucinda Kirkpatrick, PhD Researcher in Forest Ecology, University of Stirling

This article was originally published on The Conversation. Read the original article.