Factors influencing exotic species richness in Argentina's national parks

Effects of land-use types and the exotic species, Hypochaeris radicata, on plant diversity in human-transformed landscapes of the biosphere reserve, Jeju Island, Korea

Land-use and plant invasion influence biodiversity. Understanding the effects of land-use types and invasive plants on the ecosystem is crucial for better management and the development of strategic plans for increasing biodiversity in Jeju Island, Korea, a designated Biosphere Reserve by the United Nations Education, Scientific, and Cultural Organization. The effect of the most dominant invasive exotic species, Hypochaeris radicata, on the four land-use types of Jeju Island was investigated. Plant composition, soil characteristics, and plant diversity among four land-use types (cropland, green space, neglected land, and residential) were compared. Among the land-use types, croplands had the most diverse plant composition and the highest richness in exotic and native plant species. Croplands, such as tangerine orchards, which are widely distributed throughout Jeju Island, showed the highest plant diversity because of medium intensity disturbance caused by weed removal. The relative cover of H. radicata did not differ between land-use types. However, H. radicata invasion was negatively related with plant species richness, making this invasive species a threat to the biodiversity of native herbs present in land-use areas. H. radicata adapts to areas with a broad range of soil properties and a variety of land-use types. Therefore, it is crucial to monitor land-use types and patterns of plant invasion to guide the implementation of consistent management and conservation strategies for maintaining ecosystem integrity of the transformed habitat in Jeju Island.

Surprisingly high economic costs of biological invasions in protected areas

Biological invasions are one of the main threats to biodiversity within protected areas (PAs) worldwide. Meanwhile, the resilience of PAs to invasions remains largely unknown. Consequently, providing a better understanding of how they are impacted by invasions is critical for informing policy responses and optimally allocating resources to prevention and control strategies. Here we use the InvaCost database to address this gap from three perspectives: (i) characterizing the total reported costs of invasive alien species (IAS) in PAs; (ii) comparing mean observed costs of IAS in PAs and non-PAs; and (iii) evaluating factors affecting mean observed costs of IAS in PAs. Our results first show that, overall, the reported economic costs of IAS in PAs amounted to US$ 22.24 billion between 1975 and 2020, of which US$ 930.61 million were observed costs (already incurred) and US$ 21.31 billion were potential costs (extrapolated or predicted). Expectedly, most of the observed costs were reported for management (73%) but damages were still much higher than expected for PAs (24%); in addition, the vast majority of management costs were reported for reactive, post-invasion actions (84% of management costs, focused on eradication and control). Second, differences between costs in PAs and non-PAs varied among continents and environments. We found significantly higher IAS costs in terrestrial PA environments compared to non-PAs, while regionally, Europe incurred higher costs in PAs and Africa and Temperate Asia incurred higher costs in non-PAs. Third, characterization of drivers of IAS costs within PAs showed an effect of environments (higher costs in terrestrial environments), continents (higher in Africa and South America), taxa (higher in invertebrates and vertebrates than plants) and Human Development Index (higher in more developed countries). Globally, our findings indicate that, counterintuitively, PAs are subject to very high costs from biological invasions. This highlights the need for more resources to be invested in the management of IAS to achieve the role of PAs in ensuring the long term conservation of nature. Accordingly, more spatially-balanced and integrative studies involving both scientists and stakeholders are required.

Determinant Factor of Plant Species Diversity in the Organic Agriculture-Dominated System of Gedeo Zone, Southern Ethiopia

Agricultural intensification is a major challenge for biodiversity conservation in many parts of the world. Organic agriculture is perceived as a possible solution for biodiversity conservation in agriculture dominant systems. This study aimed at investigating the current status of plant species diversity and its determinants in organic agriculture-dominated areas of Gedeo zone, Southern Ethiopia. Multistage sampling procedures were used to obtain 108 households from three agroecological zones of the study area, and plant species data were collected from the quadrants laid in farms of sampled farmers. Besides, diversity management practice data were collected using focus group discussion. A total of 234 plant species belonging to 82 plant families were identified. Most (69.2%) of species in the system were native. The mean value of richness and Shannon index evenness for the whole system was 10.36, 2.06, and 0.89 for highland midland and lowland agroecological zones, respectively, which is relatively high compared with other agriculture-dominated systems in the tropics. The diversity of overall plant species were significantly affected by both agroecological zones and the wealth status of farmers. Midland and lowland agroecological zones had the highest richness values for total plant species than highland. Similarly, highest richness was recorded among farmers of rich and medium wealth classes than poor. The diversity of tree species was significantly affected by both agroecological zone and wealth status of farmer households. The lowland agroecological zone had a significantly higher number of tree species than midland and lowland agroecological zones, while the rich farmer had higher tree diversity compared to medium and poor farmers. The study also identified that diversity of shrubs were significantly influenced by agroecological zone. The midland agroecological had a significantly higher number of shrubs diversity compared to lowland and highland agroecological zones. In this study, herbaceous species diversity was not influenced by both agroecological zone and farmer wealth class. The function of plant species and indigenous plant species maintenance practice had its own effect on plant species diversity in the study area, since the area is dominated with organic agriculture. Therefore, to maintain the current status of the system and to improve the farmer’s livelihood, development planners may need to design agroecological-based plant species conservation strategies that give due consideration for indigenous plant species conservation practices and function of plant species.

Explaining the Geographic Pattern of Plant Invasion in 67 Nature Reserves in China

Biological invasion is a serious threat to biodiversity and ecosystem function in nature reserves. However, the knowledge of the spatial patterns and underlying mechanisms of plant invasions in nature reserves is still limited. Based on a recent dataset on both invasive and native plants in 67 nature reserves of China, we used correlation, regression, and variation partitioning methods to statistically assess the relative roles of the “human activity,” “biotic acceptance,” and “environmental heterogeneity” hypotheses in explaining the geographic pattern of plant invasion. A total of 235 invasive plant species were compiled from 67 nature reserves. The high explanatory power of the human activity variables supported the human activity hypothesis. The biotic acceptance hypothesis was weakly supported since no significant correlations between climatic variables and invasion levels were found when the effects of the other factors were controlled. The environmental heterogeneity hypothesis was partially supported, since the number of native plants, representing environmental heterogeneity at fine-scale explained remarkable proportion of spatial variance of invasive plants but not that of the proportion of invasive plants. We predict that nature reserves with high plant diversity affected by rapid economic development and increasing temperature will face a serious threat of exotic plant invasion. In conclusion, our results provide crucial clues for understanding geographic variance of plant invasion in China’s nature reserves and spatial risk assessment.