A recent study indicates that certain plant species like oak, hazel, and yew thrived in Europe’s forests prior to the arrival of modern humans, implying that ancient plant life was not as dense and shaded as commonly believed.
In 2023, researchers from Aarhus University in Denmark discovered that light woodlands and open vegetation were dominant in Europe’s temperate forests before the era of Homo sapiens.
A newly published study in the Journal of Ecology offers a deeper understanding of these forests’ makeup.
The findings reveal that European wildwoods had a rich presence of hazel, oak, and yew—species that flourish in dynamic, semi-open ecosystems as opposed to traditional thick forests.
“We often envision established forests as compact, shadowy areas where light-loving plants like oak and smaller species like hazel and yew are uncommon. Our findings challenge that perception, showing oak, hazel, and yew thrived continuously in these archaic woodlands, portraying a landscape of semi-open, mosaic-like vegetation,” says Dr. Elena Pearce, the lead author and postdoc at the DNRF Center for Ecological Dynamics in a Novel Biosphere (ECONOVO), Department of Biology, Aarhus University.
Plants as indicators
The research team viewed oak, hazel, and yew as indicators or “detectives” of ancient forest ecosystems, uncovering details about the structure of past woodlands.
For example, hazel produces more pollen and flowers in sunlit areas, oak vigorously regrows after being browsed, and yew, while somewhat shade-tolerant, thrives best in semi-open environments to avoid competition from taller trees. All three species tend to decrease in height-dominant, shady forests. Additionally, yew is highly sensitive to fire but can coexist with large herbivores like horses and oxen, likely due to its toxicity, which helps deter extensive browsing.
Large herbivores as natural landscape sculptors
The researchers applied the REVEALS model to conduct pollen-based reconstructions, examining the abundance of oak, hazel, and yew during two significant periods: the Last Interglacial (129,000-116,000 years ago) and early to mid-Holocene (8700-5700 years ago). Refer to the fact box for additional details.
By delving into forest compositions, the researchers discovered that open and semi-open vegetation nurtured diverse combinations of species that would have struggled to survive in closed-canopy environments.
Rather than attributing the openness to natural fires or climate factors, the new findings suggest that large herbivores were pivotal in maintaining open and semi-open landscapes. Yew’s vulnerability to fire points out this role, as it would have had difficulty thriving in fire-prone regions but managed to persist in ancient woodlands likely maintained by herbivores.
“These species demonstrate that ancient forests were not uniformly populated with towering, shade-providing trees but must have included a dynamic blend of open, semi-open, and closed areas, creating various habitats,” states Professor Jens-Christian Svenning, the senior author and director of ECONOVO.
Lessons from the past for modern nature management
The study’s findings extend beyond historical ecology. Semi-open woodlands likely played a vital role in Europe’s biodiversity, fostering habitats for species adapted to various conditions.
“Our results offer a new viewpoint on ancient ecosystems and underline the importance of preserving semi-open woodlands today. These areas support a diverse array of flora and fauna, and understanding them can inform rewilding initiatives,” explains Dr. Pearce.
The research also emphasizes the potential of open, dynamic woodlands in enhancing climate resilience and increasing biodiversity.
“As we confront global challenges like rising temperatures, extreme climatic events, and increasing tree pest invasions, fostering dynamic, diverse woodland mosaics is likely to yield stronger ecosystem functions and biodiversity advantages compared to typical dense forest plantings,” Professor Svenning remarks.
Semi-open forests promote a variety of plant species, which in turn fulfill essential roles such as carbon storage, habitats for pollinators, and broader biodiversity preservation. Strategies for reforestation that recreate these semi-open, dynamic woodland structures are likely more effective in addressing future climatic and ecological challenges, guiding sustainable forest management efforts in Europe and beyond.
