Explainer-How climate change is fuelling wildfires in Europe

By Kate Abnett

BRUSSELS (Reuters) -Wildfires have scorched hotspots in several Mediterranean countries this month, with blazes forcing thousands of people into lockdown in Catalonia in Spain, and encroaching on France's second-biggest city of Marseille.

Here's what drives wildfires across Europe, and the situation so far this year.

HOW BAD IS IT THIS YEAR?

Wildfires have burnt 227,000 hectares of land since the beginning of the year - more than double the average for this time of year over the past two decades, according to the EU's European Forest Fire Information System.

While far above average, it's not the highest in EFFIS' records, which go back to 2002. Europe had particularly bad fire seasons in 2003 and 2017, when blazes burnt more than 1,100,000 hectares in each year - an area equivalent to the island of Jamaica.

It's not yet clear if 2025 will be a record year, as that will depend on how the fire season evolves in the coming months.

The number of fires in Europe has also surged this year so far, with 1,118 blazes detected as of July 8, versus 716 in the same period last year, EFFIS said.

Heatwaves in Europe earlier this month stoked blazes around the Mediterranean, including in Syria, where fires have burned through more than 3% of the country's forest cover, according to the U.N. In the Greek islands of Evia and Crete, wildfires this month forced thousands of people to evacuate their homes.

But while Europe overall has seen a jump this year, scientists observing the fires say those in the Mediterranean region have, while destructive, so far been relatively isolated.

WHAT'S DRIVING IT?

Scientists say the Mediterranean region's hotter, drier summers put it at high risk of wildfires. Once fires start, plentiful dry vegetation and strong winds in the region can cause them to spread rapidly and burn out of control.

Climate change exacerbates this risk, by creating hotter and drier background conditions. In the countries bordering the Mediterranean Sea, that has contributed to the fire season starting earlier in recent years, breaking records for the intensity of fires, and burning more land.

Greenhouse gas emissions, mainly from burning coal, oil and gas, have heated the planet by about 1.3 degrees Celsius since pre-industrial times. Europe has warmed at twice the global average since the 1980s, according to the World Meteorological Organization.

That warmer baseline means higher temperatures can be reached during heatwaves, which climate change is also making more frequent. This has been confirmed by the United Nations' global panel of climate scientists, the Intergovernmental Panel on Climate Change.

REST OF SUMMER

Countries are preparing for worse blazes. Warmer-than-average temperatures are forecast across Europe in August, EFFIS said, meaning fire danger will remain high across much of southern and eastern Europe.

While Southern Europe is expected to see normal rainfall patterns, the rest of the continent is expected to be drier than normal in August, EFFIS said - potentially exacerbating fire risk in other regions.

Governments are attempting to adapt. Greece has assembled a record high 18,000 firefighters this year, in anticipation of severe blazes, and has adapted its firefighting tactics and patrols to attempt to detect fires earlier and limit the damage, the government has said.

Other factors exacerbate fire risk, including forest management. Shrinking populations in rural areas of countries including Spain, as people move to cities, have left smaller workforces to clear vegetation and avoid fuel for forest fires building up.

The U.N. has urged governments to invest more in prevention, rather than focusing mainly on response after fires break out - and it has warned that climate change is expected to increase extreme fires globally by up to 14% by the end of the decade.

Fire prevention can include setting controlled fires ahead of the summer season, to clear out fuel that blazes can feed on, and restoring wetlands and peatland ecosystems, the U.N. said.

(Reporting by Kate Abnett; Editing by Hugh Lawson)