1a: Connecting landscapes: Biodiversity in Linear Landscape Elements

1a:     Connecting landscapes: Biodiversity in Linear Landscape Elements

Conveners:     Constant Swinkels (Radboud University)

                        Nils van Rooijen (Wageningen Environmental Research)

                        Saskia Klumpers (Naturalis Biodiversity Centre)

1. Understanding the effects of linear landscape elements on flying insect biomass, abundance and diversity in agricultural landscapes

Robin Lexmond, Radboud University

Biodiversity has declined strongly in rural landscapes characterized by intensive agriculture. A way to restore some of the lost biodiversity in these landscapes is the creation of new landscape elements, such as hedgerows and flower strips. However, their effect on insect biomass has not been studied in this context, yet. The evaluation of caught insect biomass is complicated by strong weather effects on insect activity.

Over 3 years we studied flying insect biomass by placing malaise traps at agricultural field edges with or without hedges or flower strips in the Ooijpolder and surrounding areas. We use Bayesian statistical modelling to account for weather effects on caught insect biomass over this period. This approach allows us to quantify the effects of hedgerows and flower strips on flying insect biomass.

Results show that field edges with hedgerows harbor the highest insect biomass, whereas field edges without any natural measure present the lowest amount of caught biomass. This study demonstrates that such landscape elements, evaluated here 15-20 years after their implementation, can be a vital tool for increasing insect abundance in an agricultural landscape.

2. The potential of dikes as linear corridors

Carla Grashof, Nils van Rooijen, Friso van der Zee, Wageningen Environmental Research

In deltas, dikes play an important role for water safety along rivers and along the coast. The focus in construction and management of dikes is on strength and erosion resistance. Consequently, many dikes have a very species-poor grass vegetation. Earlier research already indicated that species diversity contributes to both biodiversity and potential strength of dikes. Current research uses innovative techniques to elaborate further on these insights. The huge length of dikes in the Netherlands provides high potential for biodiversity in delta areas as they form corridors along rivers and coasts. Also connections between coast and hinterland are possible. This presentation will highlight three important aspects of creating biodiverse dikes: construction, management and seed sources.

3. Sow Native Cornflowers: Cultivars Fall Short for Pollinators

Sophie Paquin, Radboud University

Pollinator restoration projects in linear landscape elements often aim to increase floral availability to the use of seed mixtures, sometimes including cultivars of native species. This raises the question of the importance of exclusively using native species, which are expected to benefit pollinators more than their selectively bred counterparts. This study aimed to determine if native cornflower (Centaurea cyanus), a species widely used in conservation projects in the Netherlands, differs in morphology and floral reward from cornflower cultivars, and whether these differences affect pollinator visitation in varying landscape settings. Although there were few significant morphological and floral reward, we show that native cornflower attracted on average at least twofold more visitors than the cultivars at the plant level, and 1.5 times more at the floral unit level. While further research into this mechanism is warranted, the higher visitation rates support the idea that native cornflowers are more attractive to pollinators.

4. Artificial structures enhance marine biodiversity along Dutch sea-dikes

Jorien Rippen, Lucía Irazabal Gonzales, Martje Birker-Wegter, Britas Klemens Eriksson, University of Groningen & Van Hall Larenstein university of applied sciences

Marine construction homogenizes coastal ecosystems by replacing a diverse array of shoreline habitats with artificial hard structures, such as seawalls and jetties. Climate adaptation will further increase shoreline hardening, posing an additional threat to coastal biodiversity. This study explores how artificial substrates can support biodiversity by enriching a Dutch sea dike with artificial tidepools and subtidal reefs. Biodiversity development was monitored across various tidepool and reef types over three years, with sessile communities rapidly colonizing—up to 70% coverage on reefs within the first nine months. Diverse reef types fostered greater taxonomic variation, and tidepools showed 20% higher benthic diversity than comparable dike habitats. Biodiversity benefits increased with scale, as diversity across tidepool clusters was 60% higher than in comparable sea dike habitats. These findings suggest that artificial tidepools and reefs can play an important role in management interventions to increase habitat heterogeneity and enhance marine biodiversity on modified shorelines.

5. Reseeding the new Afsluitdijk, saving a century old vegetation

Nils van Rooijen, Ben Bruinsma, Joop Schaminée, Dennis Wansink, Sophie Lauwaars, Wageningen Environmental Research

Linear landscape elements, such as dikes and road verges, often harbour endangered plant species, but as they frequently serve infrastructural purposes, nature conservation is often secondary. However, the renovation of the iconic Afsluitdijk demonstrates how biodiversity can be integrated into large civil-engineering projects. This century-old dam, which seals off the former Zuiderzee inlet, required fortification, necessitating the removal of existing vegetation, including several red-listed species and crop wild relatives. To facilitate plant regrowth, a new dike revetment was designed, but with no natural seed sources available, seeds needed to be collected before construction began. In collaboration with The Living Archive (Het Levend Archief), researchers conducted a study to safeguard the Afsluitdijk’s indigenous seeds. Innovative methods were developed to preserve and reintroduce these endangered native plants onto the new dam. This approach ensures that biodiversity conservation is less compromised, even in major infrastructure projects, providing a sustainable model for future developments.