There are several reasons why Svend Brodersen has chosen to plant thousands of trees at Gram Castle.

From: Janni Granger and Laura Attrup Bille, Innovation Center for Organic Farming

In recent years, thousands of trees have been planted on the grounds of Gram Castle to increase biodiversity and create a more climate-friendly, resilient agricultural production without compromising productivity.

At the same time, efforts are being made to preserve old trees in, for example, living hedges, which are of great value for biodiversity and provide researchers from Aarhus University with a good basis for collecting data.

Svend Brodersen, an organic farmer and owner of Gram Castle, launched a large planting project in 2024 on the castle's 3,500 hectares. Over 3,000 trees were planted by hand in a well-planned design that aimed both to ensure continued efficient operation of the land and to establish a strong foundation for a more climate-friendly, resilient organic agricultural production with good conditions for biodiversity.

The seven species and 30 varieties of trees, such as hazelnut, walnut, true chestnut, apple, pear, and plum, were selected in collaboration with nurseries and the Nordic gene bank of Pometet at the University of Copenhagen. Since then, forest farming has expanded on several areas with deciduous trees.

"My goals for forest farming were from the start that it should climate-proof our soil, sequester carbon, create high biodiversity, increase pollination in the fields, generate positive synergies from fungi on the roots of the trees, and provide shade and shelter for our cows," says Svend Brodersen.

"Furthermore, it was important that the establishment could be carried out efficiently, that we could maintain rational field operations, that we wouldn't need to fence, and that in the long run, we could generate additional income from the fields through crop sales. For us, planting trees in agriculture makes a lot of sense. All of Denmark should transition to forest farming."

Research on the effects of forest farming

On the grounds of Gram Castle, it is not only insects, birds, and wild small animals that crawl around among the trees in the living hedges. Researchers and PhD students from Aarhus University are often seen investigating biodiversity in, under, and around especially the older trees.

"What is particularly interesting about forest farming is that the trees contribute with continuity, living and dead wood, a large amount of organic matter, and a physical structure that creates a microclimate highly beneficial for biodiversity," says Marianne Bruus, senior researcher at Aarhus University.

She is involved in the project 'Biodiversity and Ecosystem Functions in Forest Farming Systems (BEAT)', which specifically examines the diversity of pollinators, soil fauna, mycorrhizal fungi, bacteria, and birds in forest farming compared to monoculture farming, analyzing carbon storage, pollination, soil functionality, and health in and around forest farming.

This is done by taking a series of samples and analyses several times a year over four years in the living hedges and at points up to 50 meters into the fields.

"We record, for example, the number and diversity of bees, hoverflies, and butterflies, earthworms and springtails in the soil, as well as soil microbiology in the form of fungi and bacteria. Additionally, we count the number and species of birds throughout the year and compare with national records. We also measure, among other things, the carbon storage in the trees and the pollination potential of crops at different distances from the trees," says Marianne Bruus.

Beneficial insects need trees

Trees integrated into agricultural land can have positive effects on crops by creating optimal habitats for beneficial insects that support optimal pollination. Moreover, many insects have important functions as biological pest controllers, and their presence, along with the trees, forms the basis for various birds and wild small animals to thrive in the agricultural landscape.

Trees and shrubs in forest farming create permanent habitats and resources in the agricultural landscape, which beneficial insects depend on. Pollinating insects need food throughout the season in the form of nectar and pollen, which trees and shrubs can provide when crops are not flowering. Many larvae also need continuous access to living and dead plant material, which understory plants can supply.

Furthermore, insects need places with shade and shelter where they can build nests and overwinter, as well as find nesting materials such as leaves, clay, and straw. The lifestyle of insects means they do not get all their needs met in, for example, flower strips, making living, permanent hedges essential.

The ground flora in forest farming also has a significant impact on biodiversity, and a permanent cover of native flowers and herbs has a highly beneficial effect.

"It is easier to demonstrate increased plant biodiversity than that of mobile species such as insects, birds, and mammals, and there are many interactions between different forest elements and crops in crop rotation, as well as grazing animals and mowing," says Marianne Bruus, adding:

"What we have so far recorded in the counts are a large number of birds, many of which are actually associated with forests. These birds are entirely dependent on the presence of trees as habitats. We can also see that the number of earthworms on the field surface depends on crop rotation, but that the number remains high under the trees over the years."

"Supports all agendas"

At Gram Castle, forest farming is here to stay, and Svend Brodersen views the many effects that forest farming is expected to contribute to biodiversity, climate, animal welfare, clean drinking water, water quality in fjords and waters, and not least the good life in everyday life on the organic farm very positively.

"For us, forest farming helps all agendas and can be part of the solution to address the major climate and biodiversity challenges we face. We have the opportunity to use the land we have available here to make a real difference, sequester a large amount of CO2 in the trees, improve the welfare of our dairy cattle by creating shelter and shade, create habitats for micro-life and wild animals, and generally lay the best foundation for a diverse soil and responsible organic agricultural production."

The project is supported by the Organic Farming Foundation and the Green Development and Demonstration Program (GUDP) under the Ministry of Food, Agriculture, and Fisheries. It is part of the Organic RDD program, coordinated by ICROFS.

Find more articles on the topic of forest farming at icoel.dk