Persistence of grassland plants - Site, landscape and species properties influencing extinction and persistence of plants in semi-natural grasslands in south Sweden

Abstract

Semi-natural grasslands in Scandinavia have been created by humans since many millennia ago, but the agricultural intensification in the last few centuries caused them to decline heavily. Accordingly, the biodiversity associated to these open, nutrient-poor habitats declined as well and many remnant populations are slowly declining and threatened to go extinct.

In this study, I focused on declining plant species specialized on semi-natural grasslands. I investigated their probability of persistence in relationship to species, site and landscape properties on different spatial scales. In this, I compared data from two large-scale plant inventories in Scania, southern Sweden, and combined it with information about semi-natural grasslands from the TUVA database.

The results show that the commonness of a species is the main driver of its further persistence, with rare species having a higher rate of decline. This can be explained by the Allee effect and other effects working on small and fragmented populations, but also points towards an extinction debt which is currently being paid off and stresses the need for an urgent grassland restoration and conservation. In this context, the habitat availability in the immediate surrounding area was the second strongest influence on grassland species persistence, stabilizing populations on all spatial levels. The results of this analysis also underline the importance of grassland quality and management for the survival of specialised plant species in accordance with many previous studies. Even though species with a higher demand for light are generally declining in Scania, the specialised light-demanding species used in this study had a higher probability of persistence within the grasslands compared to the species preferring more shady areas. While species adapted to dry environments were more likely to persist on a regional scale, species adapted to more moist habitats seemed to increase the persistence of plant occurrences in those grasslands providing a higher amount of wet area. These results indicate that even though most specialised grassland species prefer light and dry conditions, it is also important to preserve areas in which species adapted to more shady and wetter environments can persist.

Popular Abstract

What to do to help plants survive in grasslands

Semi-natural grasslands include for example pastures which are grazed by cows or sheep and meadows which have to be mowed. This active management by humans is important for the health of the grasslands and responsible for the high amount of plant species that like to live in them. However, during the last few hundred years a lot of the long existing semi-natural grasslands were turned into fields or forests. Some plant species therefore lost their homes and are declining in their distribution.

I wanted to find out if there is anything that makes it easier for those species to survive. For this I looked at examples of plants which remained in the same place for several years and examples where plants disappeared. This approach helped me to understand which characteristics of the landscape, the site or the species itself were influencing its survival.

We need to act fast!
I found that species which are rare disappear much quicker than species which are still more widespread, regardless of where they occur. The current conditions are not good enough for those species to stay around and they may soon go extinct if we do not improve their living conditions. Even for those species which are still more common it is important that we act fast, otherwise they might decline and disappear just as well.

What can we do?
According to my results the plants survive the best when there is a lot of semi-natural grassland in the landscape surrounding the site where they are. This means that they would overall need bigger, more and more connected grasslands in order to persist. A good quality of the grassland is also benefitting those species, which makes it important that we continue to let animals graze on the pastures and mow the meadows. I further found that it is good if a semi-natural grassland is not just completely dry, but also has some wetter parts. In those grasslands a lot of different species with different preferences can survive. There are some species which like it a bit shadier, but they seemed to be struggling in well-managed grasslands. We shall therefore not forget about those plants either and make sure that the grasslands we have or create also offer some shadier areas.

In the future it would be interesting to focus more on individual species and see if this general advice would help all of them to survive. If not, we would need to find out how we can adjust our actions to meet their specific needs.


Master’s Degree Project in Conservation Biology, 30 credits, 2024
Department of Biology, Lund University

Advisor: Ola Olsson
Biodiversity Unit, Department of Biology

• author: Graeske, Tamara
• supervisor: Ola Olsson
• organization: Degree Projects in Biology
• course: BIOM02 20232
• year: 2024
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9175867
• date added to LUP: 2024-10-02 14:22:10
• date last changed: 2024-10-02 14:22:10