Restored grasslands could take centuries to fully recover

Grasslands, once vibrant ecosystems teeming with diverse plant and animal life, are vanishing at an alarming rate. Land-use changes, urban expansion, and agricultural development have led to their decline. Abandoned grasslands can be restored through proper management, but full recovery takes longer than expected.

A study from Kobe University reveals that even after 75 years of continuous management, restored grasslands do not match the biodiversity of ancient ones. The slow return of specialized pollinators plays a key role in this delay.

These findings highlight the need to protect old grasslands, even when they serve modern purposes like ski slopes.

Why restored grasslands lag behind

Grasslands undergo massive ecological shifts when left unmanaged. Woody vegetation overtakes the landscape, reducing the diversity of native grassland species. Restoration efforts involve clearing invasive plants and reintroducing traditional management practices.

While this process improves biodiversity, researchers have found that restored grasslands still struggle to match the richness of ancient ones.

“The reasons for this are not really clear and satisfying solutions have not been proposed,” noted Kobe University ecologist Ushimaru Atushi.

Even when restored, grasslands seem unable to support the same variety of plant species as those that have been maintained for centuries. This realization led researchers to investigate the role of pollinators in the recovery process.

Pollinators and grassland recovery

Pollinators play an essential role in maintaining plant diversity. Without them, many plant species struggle to reproduce. Insect-pollinated plants, in particular, take longer to return after grassland abandonment.

Ushimaru and doctoral student Hirayama Gaku set out to examine how pollinator communities differ between old and newly restored grasslands.

The team selected ski slopes in Nagano Prefecture for their research. These sites provided a unique opportunity to study grasslands of different ages within a relatively small area.

“There is no place better suited to survey restored grasslands with very different management durations within a relatively small area than ski slopes,” noted Hirayama.

Why 75 years is not enough

The research, published in the Journal of Applied Ecology, confirms that even after 75 years, restored grasslands do not support the same pollinator diversity as ancient ones. While plant species may recover, pollinators remain less specialized and less efficient in transferring pollen.

Over time, the pollinator community gradually shifts, becoming more specialized. However, this process takes centuries rather than decades. “The finding shows that once valuable old grasslands are lost, their restoration cannot be achieved quickly,” said Hirayama.

The problem isn’t the number of pollinators – it’s their diversity. Restored grasslands welcome flies and hoverflies, generalists that mix pollen between different plants.

In contrast, ancient grasslands support more bees and butterflies, which specialize in pollinating specific plants. This specialization ensures that pollen reaches the right flowers, increasing plant reproduction success.

Strategies for restoring grasslands

Restoring grasslands isn’t just about plants; pollinators matter too. Ancient grasslands give specialized pollinators a place to thrive. Without them, rare plant species struggle.

Protecting these old ecosystems keeps biodiversity alive and flourishing. Ushimaru suggests that natural restoration alone may not be enough.

“It may also indicate that grassland restoration should not just be left to nature, but could require active human involvement such as by sowing seeds or by planting seedlings of native bee- and butterfly-pollinated grassland plants,” said Ushimaru.

This approach could speed up the recovery process, helping pollinator communities establish themselves more quickly.

Long-term conservation efforts

Restoring grasslands requires patience, commitment, and proactive strategies. The findings from Kobe University demonstrate that even a lifetime of restoration is not enough to fully rebuild lost ecosystems. Old grasslands, shaped by centuries of ecological interactions, provide irreplaceable value to biodiversity.

​This research was supported by the Japan Science Society, the Nagao Natural Environment Foundation, the Japan Society for the Promotion of Science, and the Environmental Restoration and Conservation Agency.​

The study was conducted in collaboration with researchers from the University of Tsukuba and the University of Toyama. Their work reinforces the need for long-term conservation efforts, ensuring that grasslands remain a thriving part of our natural world.

The study is published in the Journal of Applied Ecology.

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