By: Katalin Török and Melinda Halassy
Katalin Török and Melinda Halassy are restoration ecologists specializing in sandy grasslands in Central Hungary. Katalin focuses on botany, ecology, and biodiversity monitoring. Melinda, formerly Katalin’s student, took part in their first restoration experiment and is likely Hungary’s first PhD in restoration ecology. Their research aims to identify barriers to spontaneous restoration and analyze long-term ecological processes triggered by various restoration methods to find the most effective approaches. Both contribute to international ecological research (eLTER) and restoration policy (SERE), working to link scientific knowledge with public policy in ecological restoration.
HUN-REN Centre for Ecological Research, Institute of Ecology and Botany, Restoration Ecology Research Group, halassy.melinda@ecolres.hu
The ecosystem
One of Hungary’s most distinctive geological regions is the Danube–Tisza Interfluve (Kiskunság), which is an important reservoir of biological diversity within the Pannonian Biogeographical Region of Europe. Situated at the westernmost edge of the vast Eurasian forest-steppe biome, this region is part of a bioregion that extends approximately 9,000 km from Central Europe to Eastern Asia, covering more than 4.7 million km² (Erdős et al. 2022). The Eurasian forest-steppe represents Hungary’s dominant vegetation type, covering more than half of the country. Although the grasslands in this zone are sometimes misinterpreted as being heavily deforested in historic times, ecological models that integrate climate variability, topography, soil conditions, herbivory, and natural fire regimes reveal that forests and grasslands naturally coexist in a dynamic mosaic within the forest-steppe zone (Erdős et al. 2022).
The largest and most ecologically diverse areas of the region preserve the characteristic ”puszta“, which includes both sandy and alkaline grasslands, sand dune forests, and remnants of former sodic pans, marshes, fens, fen meadows, and wet grasslands. The inland sand dunes, shaped by wind action, consist of coarse-textured, lime-rich soils that are low in water and nutrients, supporting unique vegetation, including specialist plant and insect species. The sandy forest-steppe of the “puszta” consists of poplar-juniper sand dune forests and thickets, as well as open oak-dominated woodlands forming complex mosaics with both open and closed sand grasslands, all of which are considered habitats of high conservation concern by the European Commission. The driest grasslands in the region, known as ”Festucetum vaginatae danubiale“ community, are found on the crests and southern slopes of sand dunes. These grasslands are characterized by tussock-forming grasses such as the endemic grass Festuca vaginata and the protected Stipa borysthenica, interspersed with cryptogam cover of mosses, ferns, lichens, etc. and frequent patches of bare ground.
Throughout the 19th and 20th centuries, the landscape underwent significant human modifications, beginning with river regulation and drainage, followed by agricultural intensification and plantation forestry. As a result, the region is now predominantly covered by agricultural lands, forest plantations, and fragmented remnants of semi-natural grasslands. During the post-socialist transition (1987–1999), large-scale agricultural land abandonment occurred, particularly in low-productivity areas such as the Kiskunság (Valkó et al. 2016). While some native vegetation regenerated spontaneously, abandoned lands also became increasingly susceptible to invasion by non-native species. One of the most problematic invaders is Black locust (Robinia pseudoacacia), a fast-growing, nitrogen-fixing hardwood tree from eastern North America, which has spread extensively. Another notorious example is Common ragweed (Ambrosia artemisiifolia) that we will discuss below. The expansion of invasive species not only threatens native biodiversity and ecosystem health but can also have negative impacts on human health.
Restoration experiments
For the past 27 years, we have been conducting restoration experiments at the Kiskunság Long-term Ecological Research site to facilitate the recovery of sandy grasslands on lands degraded by Black locust plantations and arable cultivation. Our research focuses on the long-term effects of various treatments aimed at overcoming barriers to spontaneous grassland regeneration, assessing the positive and negative influences of the surrounding landscape, and enhancing invasion resistance through seed-based restoration.
Our findings indicate that active restoration interventions can significantly accelerate recovery. Specifically, sowing a mixture of locally sourced grass and forb species has proven to be the most effective method for initiating restoration in dry grasslands and controlling invasive species (Reis et al. 2023). Additionally, carbon amendments and mowing can serve as valuable complementary measures; however, they should be applied cautiously in invaded landscapes to avoid unintended ecological consequences (Reis et al. 2022).
The success of restoration efforts is further challenged by the presence of other aggressively invasive species beyond Black locust, including the tree of heaven (Ailanthus altissimus) and the herbaceous Common milkweed (Asclepias serica (formerly A. syriaca), which are particularly widespread in forest plantations (Csecserits et al. 2016). Even after the removal of dominant invasive species, new invasions may occur, likely due to legacy effects and the high dispersal capacity of these non-native species (Reis et al. 2023). To mitigate these negative impacts, restoration efforts should prioritize areas with lower invasion pressure or integrate early seeding of native species as a complementary strategy for invasion control (Csákvári et al. 2023, Halassy et al. 2023).
Restoration – human health links; research in progress
Enhancing public health through ecological restoration efforts can be of significant importance. Ecosystem services and direct contact with nature may contribute to this improvement (Millennium Ecosystem Assessment 2005, Marselle et al. 2021), but robust evidence is needed to establish clear links between biodiversity, ecological restoration, and human health at landscape, regional, and national scales.
In Hungary, a national project has recently been launched to investigate these nature–health connections using ecosystem condition maps and health data (https://termeszetem.hu/en). This initiative aims to identify correlations between environmental factors and various health indicators, such as the prevalence of allergies, depression, autoimmune and inflammatory diseases, and self-reported well-being. The research focuses on detecting these relationships at the sub-regional scale and in urban areas, as well as assessing the economic impacts of health conditions. A key initial focus of the project is the highly allergenic Common ragweed (Ambrosia artemisiifolia), which poses significant public health challenges throughout Europe and elsewhere.
Battling Common ragweed – for ecosystem and human health
Successes so far with reducing invasion of Common ragweed (Ambrosia artemisiifolia) are noteworthy. For starters, note that the disservices of Common ragweed are already serious and likely to get worse throughout Europe since its allergenic pollen affects one in ten people throughout the European continent. Schaffner et al. (2022) estimate that the health of 13.5 million people was adversely affected in 2015 by Common ragweed allergy in Europe alone, generating 7.4 billion euros (8.1 billion US$) in public health costs. Happily, our ecological restoration interventions have already demonstrated their effectiveness in battling this noxious annual weed (Fig. 1).
The successful reduction of Common ragweed invasion serves as a promising example of how ecological restoration can yield measurable benefits for human health. The new national-scale study aims to provide evidence-based insights into the potential interconnections between ecosystem health and human well-being. These findings could help inform policy decisions related to land management and restoration efforts not only in Hungary but also in other regions.
A potential next step is to investigate links between ecosystem conditions and asthmatic diseases. By analyzing data on general practitioner and specialist visits for asthma-related complaints, as well as the purchase of asthma-specific medications, we can correlate health trends with different ecosystem states across temporal and spatial scales (Nitschke et al. 2022). This approach will allow us to assess the broader health impacts of ecological restoration.
Moving forward, we plan to deepen our research on the relationship between ecological restoration and human health by collaborating with the Ecological Health Network and its member sites and hubs working on similar challenges. We believe that participation in an international social impact network will not only advance our research but also enhance its value and real-world impact.