Mapping Grassland Stability in the Netherlands

Taylor Craft, Anne Beaulieu, Theunis Piersma, and Ruth Howison

Grasslands that remain intact for many years become more naturally valuable for every year they are left untouched. These permanent grasslands are more valuable for biodiversity than grasslands plowed over every so often to make new grass or arable crops, Taylor Craft and colleagues at the University of Groningen reported in the scientific journal Frontiers. "From worms to black-tailed godwits, lots of organisms benefit from old grassland," Craft says. "But the registration of these old grasslands in official records leaves quite a bit to be desired."

Of all the fields used for agriculture in the Netherlands, the majority are used for feeding cows that produce milk. These fields are also home to many species of plants and animals that provide important ecosystem services such as nutrient cycling, pest control, seed dispersal, and climate regulation. In the Netherlands, one of the most intensively farmed countries in the world, little land is left for wildlife, so it is important for scientists to learn how our farmed land can also be used to give wildlife a home. In a recent study, a team of ecologists from the University of Groningen mapped agricultural grasslands within the municipality of Southwest Friesland, the most important breeding area for the Black-tailed Godwit. This map depicts not only grasslands but also shows how often each field has been used to grow annual row crops, such as maize or wheat. By keeping track of this, the researchers were able to measure how often grasslands are replaced by other crops. This indicates the stability in the use of grasslands and the conditions for the species that live there.

To add evidence to this, the researchers compared new and older grasslands by analyzing soil samples in the laboratory and measuring plant diversity in the fields. Both soil and vegetation are well known to act as key indicators of habitat quality. The researchers found that both soil quality and the number of plant species increased in grasslands that had been used regularly as grasslands over the years. On the other hand, grasslands that had been used to grow crops were more likely to have poorer soils and lower vegetation diversity, even when crops had not been planted for several years. This means that grasslands could take a long time to recover, which landowners and policymakers should consider when creating wildlife protection strategies.

Not only plants and soil organisms benefit from untouched grasslands. Craft also expects that our national bird, the black-tailed godwit, also thrives better on old grassland. Craft: “Softer soils allow the birds to reach earthworms deep below the surface. However, when grasslands are frequently replaced with crops, then the soil, including the life it supports, is disturbed, requiring many years to recover.” Craft also notes that “When it comes to the conservation of a single species (i.e., the black-tailed godwit), we must consider the entire food web, which starts with understanding the soil”.

Ecologists who study these species and where they live have many different tools to keep track of how the living conditions of species (ecosystems) change across time and space. For example: observing what is going on in a field through ground surveys, satellites which collect images of the Earth surface, or historical records that show how the land was used in the past. An especially important resource for Dutch researchers is a national database which keeps track of how fields are used, known as the Basis Registratie Gewaspercelen (BRP). By carefully analysing the data over many years and using different sources of information about the fields, the researchers also discovered that the way the fields are registered in the database is not accurate enough. For example, there are quite a few fields that are identified in the database as long-term grasslands, but that have recently been used to grow annual crops. In addition, many fields are simply not registered in certain years. This has an impact on how fields are counted as grassland and shows that it is very important to examine the evidence we use carefully. Otherwise, the conclusion might be that there is more grassland than there actually is.

This study offers a new visual aid to show where older grasslands are located within the most important breeding area of our national bird. Craft and his colleagues hope that maps such as this help to convey complex ecological information in a way that is understandable not only for scientists, but for landowners, policymakers, and the public alike. It is crucial for policymakers to track and evaluate agri-environmental schemes for biodiversity management and increase the ability to protect the status of older grasslands. Farmers should be aided when maintaining their older grasslands and use the management history of their land to justify why conventional grasslands contribute to the relatively small core nature areas. Craft and his colleagues believe that nature managers can better identify corridor areas and build on their network of stakeholders when they are applying for EU funding aimed to protect ageing grasslands. By reshaping the conventional mindset of nature vs. agriculture into nature-inclusive agriculture, we can turn the tide on insect decline, re duce greenhouse gas emmisions, protect the quality of our soil and water, and ensure the human well-being of current and future generations.

Read the open access article at: https://www.frontiersin.org/articles/10.3389/fenvs.2022.982925/full