A living climate record in the central Apennines, a unique collection of old-growth European beech forests (Fagus sylvatica) stands at the southern edge of the species's natural range.%%CITE_1%%%%CITE_2%% Five of these forests, located within the Abruzzo, Lazio and Molise National Park, are so exceptional they form a UNESCO World Heritage site.%%CITE_3%%%%CITE_4%% They contain some of the oldest known beech trees in the Northern Hemisphere, with many individuals exceeding 500 years of age.%%CITE_5%%%%CITE_6%% One specimen in the Valle Cervara is over 560 years old.%%CITE_3%%%%CITE_6%% These ancient trees record climate history. Scientists use dendrochronology, the study of tree rings, to understand past environmental conditions. The width of each ring reveals the relative growth during a particular year; wider rings indicate good conditions, while narrow rings suggest stress.
Studies of these trees show a worrying trend. As regional temperatures have increased and summer droughts have become more common, the growth rates of these southern beech populations have declined. This is particularly true at lower altitudes, where trees are more exposed to heat and water stress. Over the last 60 years, the central Apennines have seen a significant increase in mean annual temperatures of about 1.7°C. A linear model based on tree ring data estimates a potential reduction in the lifespan of beech trees by about 23 years for each degree of warming.
An uncertain future
The future persistence of these forests is uncertain. The same climatic pressures that slow the growth of mature trees also prevent new ones from establishing. Successful regeneration of beech trees requires a humid atmosphere and well-distributed precipitation. The increasingly warm and dry summers are causing regeneration failure, meaning seedlings are unable to survive and grow into the next generation of trees. This failure is most pronounced at the lower, warmer edges of the forest.
This ecosystem is responding to climate change by effectively moving. As lower elevations become inhospitable, the conditions suitable for beech survival are shifting upslope to higher, cooler altitudes. The forests currently thrive at elevations between 1,400 and 1,850 meters. This upward shift is a slow process, and it is unclear if the trees can migrate fast enough to keep pace with the rate of climate change. As the climate continues to warm, these high-altitude refuges may shrink or disappear entirely, leading to a significant loss of this unique forest ecosystem and its associated biodiversity. Models project that under some climate scenarios, beech forests in southern Europe could see productivity declines of 20% to over 50% within the next 70 years.