Ecological hide-and-seek and its potential implications for conservation biology

By Tibor Hartel

Conservation biology is basically about protecting nature: its components (e.g. species, habitats) or whole landscapes. To do this, ecologists most often use lists of rare / vulnerable species and ‘habitats’. These species and habitats are identified during field surveys and various areas are delineated in order to ‘control’ human impact on them and ultimately to assure their ‘long term persistence’. Areas without species and habitats of conservation concern may be valued by conservationists, but generally are not on the top of their priorities. These areas are generally exposed to increasing human impact.

Some (rare) species may invite ecologists to a real ‘hide-and-seek’ game when is about finding them. If not identified, these species may be declared as absent from the sites (and the sites may not receive protective status), but in reality they may be quite abundant there. Many rare plant species may pose such a challenge for ecologists. Rural landscapes are shaped by human activity, which may be century long. Low intensity grazing often result in grasslands with high nature value character, containing many rare plant, insect and other animal species. Grazing abandonment may change the species composition and vegetation structure of these grasslands through a number of synergistically interacting factors such are the accumulation of litter and the chemical compounds released by the litter. These may change the micro-environment of the seeds of rare plant species in a way to inhibit germination for long periods of time (i.e. decades). To put shortly: abandonment of grazing may reduce species diversity in these grasslands in long term.

In this respect Eszter Ruprecht and her colleagues published an interesting paper in Biological Conservation. They studied steppe like grasslands in a rural landscape from Transylvania (Romania), after ~40 years of grazing abandonment. These grasslands contain many rare plant species and are priority habitats of the Habitats Directive of the European Union. In many areas of Transylvania these grasslands tend to be abandoned, e.g. because of the low economic profitability of grazing them. The field experiment consisted of (i) removing the litter from study plots and (ii) combined litter removal and vegetation cutting. These sites were compared with control plots (no litter and vegetation removal).

The results of this study clearly showed that the experimental treatment positively influenced the germination and seedling survival of many rare dry grassland species. Some species which were considered locally extinct re-appeared from the local seed bank exclusively due to the experimental intervention. These results indicate a high restorative potential of Transylvanian dry grasslands even after decades of land abandonment. The authors of the paper note: ‘Once studies from many different types of grasslands will become available, it will be interesting to identify whether the re-emergence of rare species is limited or characteristic to certain grassland types.’

I would like to see more such studies conducted in the Transylvanian and Eastern European rural landscapes. These landscapes now are sharply changing both because of agricultural intensification and land abandonment (see the study of Cristina Cremene and her colleagues published in Conservation Biology in 2005). While most of ecologists are more interested and concerned with the first category of problem, the effects of land abandonment on biodiversity is virtually unknown. In my opinion this study represents a good evidence for the potentially high conservation importance of the abandoned lands in Transylvanian (and potentially Eastern European) rural landscapes. This is an extra challenge for conservationists, which are now invited to play the hide-and-seek game. If we close our eyes and / or are not inventive enough to find the concealing organisms in due time, we may loose them forever. Seed banks may assure long term ecological continuity in locations where they occur e.g. as ‘ecological memory’. The consideration of ecological memory can be particularly important in the era of rapid global change which challenges the adaptability of species, ecosystems and landscapes.

References

Bengtsson, J. et al. 2003. Reserves, resilience and dynamic landscapes. Ambio 32: 389-396.

Cremene, C. et al. 2005. Alterations of steppe-like grasslands in Eastern Europe: a threat to regional biodiversity hotspots. Conservation Biology 19: 1606-1618.

Ruprecht, E. et al. 2010. Restorative removal of plant litter vegetation 40 years after abandonment enhances re-emergence of steppe grassland vegetation. Biological Conservation 143: 449-456.

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