A recent study from the University of Copenhagen [55.7°N, 12.6°E] sheds light on a crucial yet often overlooked challenge in ecological restoration: bringing life back to wetlands. Across Europe, these fragile ecosystems have been drained, farmed, and urbanised for centuries, leaving only fragments of their former selves. While restoration efforts are now in full swing, this research reveals that simply rewetting the land is not enough. To truly revive biodiversity, we must rethink how we manage nutrients, landscape connectivity, and natural grazing.
Why Wetlands Matter
Wetlands are nature’s superheroes. They filter water, store carbon, and provide habitat for an astonishing variety of plants and animals. In the UK and Denmark alike, efforts to bring them back have focused on improving water quality—reducing nitrogen and phosphorus runoff from farms. But this study suggests that focusing only on water conditions may be missing the bigger picture.
The research compared restored wetlands with near-natural ones and found that restored sites were significantly less biodiverse, with fewer plant species and a greater tendency for a small number of aggressive species to dominate. The reason? Three main culprits: excess nutrients, isolation from other wetlands, and lack of natural grazing.
Key Insights for Better Wetland Restoration
- Too Many Nutrients Can Be a Bad Thing
- Decades of farming have left a legacy of nitrogen and phosphorus in the soil, which fuels the growth of a few fast-spreading plants like reeds and rushes, pushing out more delicate wetland species.
- Even after restoration, continued nutrient runoff from surrounding farmland keeps these conditions locked in, making it hard for biodiversity to recover.
- Isolation Limits Nature’s Comeback
- Many wetlands are now islands in a sea of agriculture, meaning plants and wildlife struggle to migrate back once a site has been restored.
- Sites with a nearby patch of natural wetland fared much better, suggesting that connectivity is key—restoration works best when done in networks, not in isolation.
- The Case for Grazing
- For thousands of years, Europe’s wetlands were grazed by large herbivores, shaping diverse plant communities. But today, many restored wetlands are left ungrazed, allowing tall grasses to take over and smother smaller plants.
- The study found that grazing increased plant diversity, preventing the spread of dominant species and creating micro-habitats for wetland specialists.
Implications for other nations, such as Britain
The UK has seen ambitious wetland restoration efforts, from the Great Fen Project in Cambridgeshire to the Somerset Levels rewetting initiatives. Yet, as this research shows, simply reflooding land is not enough to restore complex ecosystems. To get it right, we need to:
- Prioritise nutrient control—not just stopping new pollution but actively removing legacy nutrients where possible.
- Create connected wetland corridors, ensuring that restored sites are not isolated but form part of a wider landscape.
- Reintroduce natural grazing, using low-density livestock or rewilding approaches to mimic the lost role of wild herbivores.
A Path to Thriving Wetlands
This study offers an urgent yet hopeful message: wetland restoration works—but only when done right. By addressing nutrient overload, ensuring connectivity, and restoring natural grazing, we can help wetlands flourish once again, bringing back the biodiversity and resilience they once provided.
Source
Nutrients, Isolation, and Lack of Grazing Limit Plant Diversity in Restored Wetlands, Journal of Applied Ecology, 2024-01-24
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