Semi-natural grasslands are often habitats dominated by a high diversity of indigenous plant species, which are characterized by their small size and tolerance for disturbance. The long-term history of the emergence of these plants is not fully known, but it is well known that they cannot survive without moderate disturbances that keep their tall and fast-growing competitors away. This habitat continuum is being maintained by traditional, non-intensive agriculture with extensive livestock grazing and mowing activities.
In the present industrialized world driven by economic realities, the intrinsic value of biodiversity is not fully recognized and this low-intensive agriculture is often regarded as a non-profitable use of land. As a consequence, the once wide network of extensively managed, semi-natural grasslands has been reduced to a set of small and isolated patches relatively far apart from each other. There’s no easy way to define how detrimental this fragmentation is, but many researchers agree that the present network of semi-natural grasslands is not enough to ensure the long-term protection of this specialized species pool.
Increasing the area of semi-natural grasslands can be accomplished through restoration—re-introducing native plant species back to the locations where they previously existed. However, as restoration is a slow and time consuming process with little guarantee of results, it is important to rationalize the selection of the most suitable targets. Long-term, continuous grazing and/or mowing on open or partly open grasslands is recognized as an essential precondition to inhibit a build-up of soil nutrients and prevent fast growing, competitive species from achieving dominance. Best restoration targets are found in locations that have not been intensively fertilized for crop production and have retained some of the initial semi-natural vegetation, either as living plants or as a viable seed bank.
In the process of selecting restoration sites, spatial data such as historical maps and old aerial images may be of substantial help. Of course, they offer only snapshots of historical development and are limited by potentially poor accuracy, but the power of spatial data should not be underestimated. Fieldwork for decision making about restoration is always needed, but because signals from the past are often faint, pre-knowledge of the landscape can be highly beneficial.
Using GIS software and a set of georeferenced historical layers, an overlay analysis and classification of landscape trajectories can be performed. These results can be further utilized for detecting potential restoration targets and estimating larger landscape-scale scenarios for the semi-natural grassland network. Trajectory classification and scenarios based on this data do not replace field work but help in the pre-estimation of suitable locations and reduce chances of missing important grassland patches.
Increasing the area of managed semi-natural grasslands should be made a priority in order to reach the goals set for biodiversity preservation in northern Europe and other areas where grasslands provide important habitats. And while uninterrupted management of existing sites is essential for ensuring the stability of the habitat network and reaching the favourable conservation status, restoration actions are of equal importance. When fieldwork is coupled with GIS-oriented landscape trajectory analysis, restoration attempts will be maximised.
Existence and quality of historical data is highly dependent on the study site, and trajectory analysis always requires a certain degree of creativity, but the knowledge provided of the past landscape helps to make better restoration decisions and should be regarded as an essential tool for restoration planning.
Images by Timo Pitkänen
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