Spread Of Invasive Alien Plants Research Articles

Maternal effects of human-mediated disturbances on the growth and reproductive traits of different ecotypes of an annual invasive plant Erigeron annuus

A multifactorial combination of human-mediated disturbances is now recognized as a major driver of the global rise and spread of invasive alien plants. Among the numerous invasive alien plants, annuals have fast adaptability and evolution via maternal effect in human-mediated disturbance environments, such as chemical and physical controls. The characteristic enables them to quickly disperse and establish new habitats. Thus, understanding the adaptability and evolution of invasive plants in response to multifactorial human-mediated disturbances is crucial for developing effective management strategies to control their spread and minimize their impacts on ecosystems and human activities. In order to test the growth and reproductive responses in both the parent and offspring generations, two ecotypes (clump and scatter) of an annual invasive plant, Erigeron annuus, were subjected to simulated trampling, defoliation (simulated herbivory), and herbicide disturbances. We found that disturbances negatively affected the growth and reproduction of E. annuus in parent and offspring generations. In comparison to the scatter ecotype plants, the clump ecotype plants had greater growth and reproductive production, as well as a reduced maternal interference effect to cope with human-mediated disturbances. It enhanced the adaptability of their offspring to disturbances. The findings imply that the evolutionary advantage of clump ecotype plants may explain why they can thrive in disturbed habitats and become invasive in some regions.

Visitors’ Environmental Impact on Conservation Areas: An Evaluation of Annapurna Base Camp Trekking Trail in the Annapurna Conservation Area, Nepal

Worldwide, natural landscapes possessing exceptional biodiversity are declared as protected areas for conserving unique biodiversity and ecosystems. With the invention of the concept of ecotourism, protected areas have been established as the most preferred nature-based tourism destinations. The increased tourism activity within the conservation area generates many negative environmental impacts which eventually deteriorate the ecosystem and threaten the biodiversity. The Annapurna Conservation Area is a mountain ecosystem providing shelter for various unique biodiversity and is also famous for tourism activity. Annapurna Base Camp Trekking trail within the Annapurna conservation area has been established as one of the most preferred trekking destinations, however, the negative environmental impacts of tourism on this trekking trail are yet unknown. In this study, we evaluated the environmental impacts of tourism across the Annapurna Base Camp Trekking trail via field visit observation, group discussion, and questionnaire survey on a Likert scale ranging from one to five. The result revealed that solid waste generation and the spread of invasive alien plants across the trekking trail are the obvious environmental impacts of tourism while impacts on other aspects of the environment are almost insignificant and within the threshold limit. The findings thus indicate the need to devise an effective strategy for mitigating solid waste generation and preventing the spread of invasive plants. This finding provides important insights to formulate policies for the management of tourism in conservation areas and protect the biodiversity, landscape, and ecosystem of the Annapurna Base Camp Trekking trail and other similar trekking destinations across the entire country.

A phyto-guide to species selection for optimized South African green infrastructure

In South Africa, rapid environmental degeneration caused by anthropogenic pollution poses a major ecological engineering problem, demanding proper resource mitigation strategies. For the treatment of polluted water and degraded soil systems, green infrastructure (GI) offers an effective, sustainable and affordable nature-based alternative to grey infrastructure. An additive benefit within GI, plant species provide enormous potential to treatment; however, species vary substantially in their pollutant removal and hydrologic performance. South African civil engineers tasked with designing GI often lack expertise and knowledge of plant behaviour and ecosystem dynamics. Therefore, this paper proposes a decision framework to facilitate selection for designing local GI in the form of a phyto-guide, based on existing recommendations and knowledge of removal processes and plant behaviour. Interdisciplinarity at the core of the phyto-guide relies on continuous specialist collaboration with each selection criteria, whilst efficiency and sustainability are considered equally important contributors to successful GI functioning. The spread of invasive alien plants, whether accidental or deliberate, negatively impacts an ecosystem’s capacity to deliver goods and services. Thus, the desire to optimize GI by incorporating effective phytoremediators cannot be prioritised over conservation concerns. In addition, this paper seeks to advance the GI limitation of relying solely on previously identified phytoremediators, by including evaluation criteria of beneficial plant traits as well as plant distribution, behaviour and diversity into the decision-making process for optimized GI. It is recommended that future research engages in discovering less invasive, naturally occurring local species as potential phytoremediators, inspired by South Africa’s rich biodiversity and endemism, as well as conveying the importance of consultation with engineers and ecologists for optimized GI.

Impacts of invasive alien plants on ecosystem services of Ramsar lake cluster in middle mountain Nepal

Biological invasions have significant impacts on ecosystems, the services provided by ecosystems, and associated economies. In wetlands, invasion by alien plants can impact the ecosystem services that are fundamental to human well-being. We conducted a stakeholder analysis in Ramsar sites in the Pokhara Valley to understand ecosystem services, the economic valuation of provisioning services, invasive alien plants, and their impacts. We collected information from locals living near the Ramsar site using focus group discussions, key informant interviews, and household (HH) surveys. We identified five invasive alien plants in the Ramsar sites in Pokhara Valley. A total of 18 ecosystem services were recorded from discussions with residents living near the Ramsar sites. Our study found that the economic benefits generated from the provisioning service, calculated based on the market price in the year of data collection, were worth a total of International$ 9.05 million. The value of provisioning services was International$ 0.1 million HH−1 year−1. Our estimate showed that the value of provisioning services before the occurrence of invasive alien plants in 1989 was International$ 0.19 million HH−1 year−1 higher than in 2019. Those who benefit from the Lake clusters mentioned that the invasive alien plants led to a decrease in economically important plants such as medicine and fruits and decreased fish production. Other impacts have included: reduced natural beauty, loss of biodiversity, and obstruction of recreational boating, which has discouraged tourism in recent years, among other impacts. Our results show that the rampant spread of invasive alien plants has a severe impact on ecosystem services. The impact on the associated economic value is alarming. There is an urgent need for proper management of wetlands. The findings from our results can help make decision-makers aware of the need to act in order to restore and maintain the services provided by the wetlands.

Modeling the geographic spread and proliferation of invasive alien plants (IAPs) into new ecosystems using multi-source data and multiple predictive models in the Heuningnes catchment, South Africa

ABSTRACT The geographic spread and proliferation of Invasive Alien Plants (IAPs) into new ecosystems requires accurate, constant, and frequent monitoring particularly under the changing climate to ensure the integrity and resilience of affected as well as vulnerable ecosystems. This study thus aimed to understand the distribution and shifts of IAPs and the factors influencing such distribution at the catchment scale to minimize their risks and impacts through effective management. Three machine learning Species Distribution Modeling (SDM) techniques, namely, Random Forest (RF), Maximum Entropy (MaxEnt), Boosted Regression Trees (BRT) and their respective ensemble model were used to predict the potential distribution of IAPs within the catchment. The current and future bioclimatic variables, environmental and Sentinel-2 Multispectral Instrument satellite data were used to fit the models to predict areas at risk of IAPs invasions in the Heuningnes catchment, South Africa. The present and two future climatic scenarios from the Community Climate System Model (CCSM4) were considered in modeling the potential distribution of these species. The two future scenarios represented the minimum and maximum atmospheric carbon Representative Concentration Pathways (RCP) 2.6 and 8.5 for 2050 (average for 2041–2060). The results show that IAPs are predicted to expand under the influence of climate change in the catchment. Concurrently, riparian zones, bare areas, and the native vegetation which is rich in biodiversity will greatly be affected. The mean diurnal range (Bio2), warmest quarter maximum temperature (Bio5), and the warmest quarter precipitation (Bio18) were the most important bioclimatic variables in modeling the spatial distribution of IAPs in the catchment. Comparatively, all the models were successful in predicting the potential distribution of IAPs for all the scenarios. The BRT, MaxEnt, and RF predicted the spatial distribution of IAPs with an Area Under Curve (AUC) of 0.89, 0.92, and 0.94, respectively. The study highlighted the importance of multi-source data and multiple predictive models in predicting the current and potential future IAP distribution. The results from this study provide baseline information for effective land management, planning, and continuous monitoring of the further spread of IAPs within the Heuningnes catchment.

Towards global dominance of invasive alien plants in freshwater ecosystems: the dawn of the Exocene?

The global and seemingly unstoppable spread of invasive alien plants emerges as one of the main topics of current science. This is due to the multiple repercussions of invasive plants on biodiversity and ecosystem functioning, plus huge consequences on human existence. In freshwaters, lots of invaders are extremely competitive by virtue of their idiosyncratic reproductive and adaptive strategies. As “inland islands”, freshwaters seem particularly prone to changes when invaded, such as reorganisation of food webs and biotic interactions. Together, these events are self-reinforcing, implying hardly reversible hysteric phenomena. The intention of this paper is to point out: invasion pathways, driving factors, invasion mechanisms, and noticeable effects mediated by plant invaders in freshwaters through an extensive knowledge review. The growing evidence suggests the dawn of a new epochal phase: a globally alien-dominated “bio-historical horizon”, tentatively called “Exocene”, where invaders play predominant roles that drive freshwaters functioning and successional unexpected stages. In the context of invasion science, Exocene reinforces the need for an ecosystem-based perspective to properly understand the implications of plant invaders in freshwaters. Seven challenging issues emerge to be addressed to better outline the global paths of biodiversity and functioning between biomes when faced with biological invasion.

Evaluating Google Street View for tracking invasive alien plants along roads

Invasive alien plants are considered a major driver of global biodiversity loss. Therefore, there is a huge demand of spatial and temporal data on their distribution for investigating possible drivers of species invasions and for predictions of future distributions. We use Google Street View imagery (GSV) as a new source of spatial and temporal data. GSV provides millions of panoramic views along road networks worldwide allowing for the identification of many plant species, including invasive ones. Thus, GSV has a great potential to support ecological research in documenting species distribution, but reliable validation of its precision and accuracy is lacking. Here, we describe and evaluate an approach using GSV to visually track the spread of invasive alien plants, the North American goldenrods (Solidago canadensis and S. gigantea) occurring abundantly along road network in Poland (Central Europe). We determined presence/absence of the species along 160 randomly selected transects of a length of 500 m by visual inspection of GSV images and compared it with field surveys at the same transects. We show that the occurrence of goldenrods in GSV is a reliable predictor of their occurrence in the wild. Sampling parameters, like road width, season when GSV pictures were taken and number of months elapsed since taking the GSV pictures, did not change the correlation between outputs of the two methods (GSV and field sampling). Furthermore, both the occurrence of goldenrods observed in the field and their occurrence in GSV have similar relations to habitat characteristics investigated (the same direction of relationship and similar effect size). We suggest Google Street View images may be an additional tool to be used in the detection and tracking of the spread of invasive alien plants along roadsides. The approach may be useful in assessing temporal changes in roadside vegetation and managing problematic plant species across large spatial scales and may contribute to the further development of more efficient sampling methods in ecological studies.

Naming Invasive Alien Plants into Indigenous Languages: KwaZulu-Natal Case Study, South Africa

The spread of invasive alien plants (IAPs) across countries does not only dilute the indigenous biodiversity richness and degrade the environmental integrity of local environments, but it also threatens human livelihoods. Although no studies have been conducted on the relationship between IAPs and indigenous knowledge on plants, contributors suspect that IAPs might have negative impacts on cultural application of indigenous plants, more especially in the case of medicinal plant use. In the province of KwaZulu-Natal (KZN), South Africa, where there are mainly isiZulu speakers, the use of plants for various human benefits is still relatively high. Plants are used for many reasons including traditional medicine, food, shelter and cultural rituals such as during burial ceremonies of family members. In certain parts of KZN, when a person is buried, a row of medium-sized logs of Black Wattle (Acacia mearnsii) are put on top of the casket to prevent soil from piling directly on top of the casket. Traditional healers rely heavily on certain plants to meet their different objectives and this now includes IAPs. Traditionally, they would use indigenous plants, which are known by their isiZulu common names but with the influx of IAPs, confusion between indigenous and alien plants has crept in.In some instances, an indigenous plant and an alien plant which resemble each other now even share the same isiZulu common name. Alternatively, there is confusion when one has to collect an indigenous plant but cannot differentiate between that and a similar IAP, which might not have an isiZulu common name (in that case it does not matter whether the IAP has an isiZulu common name or not). Additional problems arise when the intention is to propagate an indigenous species and an IAP ends up being unintentionally propagated. Furthermore, where indigenous plants have been over-utilized and become scarce to find and thus switching to an IAP that resembles the scarce indigenous plant, becomes an option. To make matters worse, when naming IAPs if the process is unregulated, IAPs are given attractive, positive names that unintentionally might create an impression that “these plants are good”. The intention of this article then was; a) To advocate for the naming of IAPs into indigenous languages and that the naming process should be structured and regulated, b) To systematically suggest names for some of the dominant IAPs within eThekwini Municipality, KZN province of South Africa, as a case study, c) To review existing isiZulu common names of some IAPs to make sure those names are not confused with those of indigenous plants (NB: Some English common names of IAPs also need to be reviewed!); d) To advocate for IAPs to be given negative names and finally, e) To facilitate the naming process and adoption of isiZulu common names for IAPs.

Invasive plants of the Kampinos National Park outskirts – the current state and threats to the protected area

Studies aimed at the identification of the range and the ways of spread of invasive alien plants in the Kampinos National Park (KNP) outskirts were carried out between 2012 and mid 2018. Special emphasis was placed on surveying the sites of the invasive species and diagnosing potential threats posed to the natural and semi-natural vegetation of the national park by them in rural areas. A floristic survey was carried out on the majority (93 localities) of settlement areas in the vicinity of KNP, in its buffer zone, frequently near the border of the park. Thirty-nine invasive taxa were found which may potentially pose a threat to the ecosystems of KNP. The most frequently identified species included trees and shrubs: Acer negundo, Rhus typhina, Robinia pseudoacacia, Partenocissuss inserta, and herbaceous plants: Conyza canadensis, Erigeron annuus, Solidago serotinoides, S. canadensis. Species encroaching from the settlement areas to semi-natural and natural communities include Bidens frondosa, Echinocystis lobata, Impatiens glandulifera, I. parviflora, Juncus tenuis, Lupinus polyphyllus, Reynoutria japonica, R. xbohemica and Solidago serotinoides. Most of them are species from the highest (III and IV) classes of invasiveness in Poland. The close distance to the Warsaw conurbation, and the road network developed around KNP has certainly affected the number of alien species recorded in the analysed area. Urbanized lands neighbouring the Park are still probably a source from where alien plants disperse to the protected area.

Invasion compounds an ecosystem-wide loss to afforestation in the tropical grasslands of the Shola Sky Islands

Tropical montane habitats, including the Shola Sky Islands in the Western Ghats, host several threatened taxa of which, the global distributions are restricted to these mountain-tops. The rapidly increasing human footprint and the spread of invasive alien plants have already resulted in the local extinction of several taxa. Here we examine the entire Shola Sky Islands ecosystem to estimate the extent of habitat loss and to create a baseline of land use in this rapidly changing landscape. We used LANDSAT imageries from 1973, 1995 and 2017, with 840 ground truth points across the ecosystem. We find substantial landscape modification in the large high elevation plateaus (7–60%) over the last four decades while changes are muted in the other parts. The loss of grasslands to exotic trees predominates (340 km2, 23%) the modification of this landscape, and, continues today at a rapid pace. Contrary to popular belief, Shola Forests have been relatively stable, implying that most plantations were established on grasslands—traditionally classified as “unproductive wastelands”. Across the Protected Area (PA) network, Reserve Forests (RF), the least protected areas have faced the greatest loss of grasslands. Older PAs have lost relatively fewer grasslands, but the invasion from adjoining RFs is now increasing. We highlight the complexity of conservation in this landscape with three case studies of PAs with different management histories. Our study highlights the rapid loss of native Shola Grasslands, the continuing loss to invasive exotic trees, and the challenges of conserving this critical habitat with traditional modes of conservation.

Do abandoned farmlands promote spread of invasive alien plants? Change detection analysis of black wattle in montane grasslands of the Eastern Cape

ABSTRACTInvasive alien plants (IAPs) pose a threat to ecosystem integrity and generally provide more disservices than services. Acacia mearnsii (black wattle) was introduced to South Africa for its provisioning and economic potential. Since then, it has colonized large areas and it is a high priority taxon by the Working for Water (WfW) programme. This study establishes the nature of the spread of A. mearnsii in grasslands in the Eastern Cape Province of South Africa, with the aim of providing feedback to the WfW programme on IAP expansion and focal areas of concern. Land cover change detection analysis using historical aerial photographs showed that A. mearnsii has spread more extensively into disturbed (abandoned cultivation and overgrazed) grasslands compared to undisturbed natural grasslands from the initial plantings prior to 1958. Using the point-centred quarter method to determine density, and an allometric equation to determine above-ground biomass, a growth model for A. mearnsii was prepared. The incremental annual increase in the standing biomass of A. mearnsii using the model, validated against MODIS Net Primary Productivity data, was estimated to be ~10.5 ton DM ha−1 yr−1. The spread rate of wattle maybe up to 10% and several alternative control strategies need to be considered.

How ecosystems change following invasion by Robinia pseudoacacia: Insights from soil chemical properties and soil microbial, nematode, microarthropod and plant communities

Biological invasions are a global threat to biodiversity. Since the spread of invasive alien plants may have many impacts, an integrated approach, assessing effects across various ecosystem components, is needed for a correct understanding of the invasion process and its consequences. The nitrogen-fixing tree Robinia pseudoacacia (black locust) is a major invasive species worldwide and is used in forestry production. While its effects on plant communities and soils are well known, there have been few studies on soil fauna and microbes.We investigated the impacts of the tree on several ecosystem components, using a multi-trophic approach to combine evidence of soil chemical properties and soil microbial, nematode, microarthropod and plant communities. We sampled soil and vegetation in managed forests, comparing those dominated by black locust with native deciduous oak stands.We found qualitative and quantitative changes in all components analysed, such as the well-known soil nitrification and acidification in stands invaded by black locust. Bacterial richness was the only component favoured by the invasion. On the contrary, abundance and richness of microarthropods, richness of nematodes, and richness and diversity of plant communities decreased significantly in invaded stands. The invasion process caused a compositional shift in all studied biotic communities and in relationships between the different ecosystem components.We obtained clear insights into the effects of invasion of managed native forests by black locust. Our data confirms that the alien species transforms several ecosystem components, modifying the plant-soil community and affecting biodiversity at different levels. Correct management of this aggressive invader in temperate forests is urgently required.

Reconstructing the spread of invasive alien plants on privately-owned land in the Cape Floristic Region: Vergelegen Wine Estate as a case study

Invasive alien plants (IAPs) are a major threat to biodiversity in South Africa’s Cape Floristic Region (CFR). Activities like agricultural development, the establishment of forestry plantations and urbanization change environments and provide opportunities for IAPs to spread. We examine the factors that have contributed to plant invasions on a privately-owned farm in the CFR. The objectives of the study were: (1) to determine what land-use changes took place that could have influenced the spread of IAPs; and (2) to document the patterns of spread of IAPs. Aerial photographs from 1938, 1966, 1977, 1989 and 2004 were used to determine the types and rates of land-use change over time. Key land-use changes involved agriculture, commercial plantations, urban development and the spread of IAPs. The spatial analysis identified the main drivers of change. Agricultural development was the main land-use change driver and affected 40% of the study area by 1977. Areas occupied by IAPs increased with land-use change from 8% cover in 1938 to 40% in 2004, and then declined to 15% in 2013 following the initiation of control operations in 2004. The study illustrated a clear link between human activities, changes in land-use and the spread and proliferation of IAPs.

A preliminary assessment of the extent and potential impacts of alien plant invasions in the Serengeti-Mara ecosystem, East Africa

This article provides a preliminary list of alien plant species in the Serengeti-Mara ecosystem in East Africa. The list is based on broad-scale roadside surveys in the area and is supplemented by more detailed surveys of tourist facilities in the Masai-Mara National Reserve and adjoining conservancies. We encountered 245 alien plant species; significantly more than previous studies, of which 62 (25%) were considered to have established self-perpetuating populations in areas away from human habitation. These included species which had either been intentionally or accidentally introduced. Of the 245 alien plants, 212 (including four species considered to be native to the region) were intentionally introduced into gardens in the National Reserve and 51 (24%) had established naturalised populations within the boundaries of these tourism facilities. Of the 51 naturalised species, 23 (11% of the 212 alien species) were recorded as being invasive within the ecosystem, outside of lodges and away from other human habitation. Currently, the Serengeti-Mara ecosystem is relatively free of widespread and abundant invasive alien plants, with a few exceptions, but there are extensive populations outside of the ecosystem, particularly to the west, from where they could spread. We address the potential impacts of six species that we consider to pose the highest risks (Parthenium hysterophorus, Opuntia stricta, Tithonia diversifolia, Lantana camara, Chromolaena odorata and Prosopis juliflora). Although invasive alien plants pose substantial threats to the integrity of the ecosystem, this has not yet been widely recognised. We predict that in the absence of efforts to contain, or reverse the spread of invasive alien plants, the condition of rangelands will deteriorate, with severe negative impacts on migrating large mammals, especially wildebeest, zebra and gazelles. This will, in turn, have a substantial negative impact on tourism, which is a major economic activity in the area.Conservation implications: Invasive alien plants pose significant threats to the integrity of the Serengeti-Mara ecosystem and steps will need to be taken to prevent these impacts. The most important of these would be the removal of alien species from tourist facilities, especially those which are known to be naturalised or invasive, the introduction of control programmes aimed at eliminating outlier invasive plant populations to slow down the spread, and the widespread use of biological control wherever possible.

Mapping Prosopis glandulosa (mesquite) in the semi-arid environment of South Africa using high-resolution WorldView-2 imagery and machine learning classifiers

The rapid spread of the Prosopis species has caused considerable negative impacts to biodiversity across different landscapes. The invasive taxa of Prosopis is currently rated the world's top 100 unwanted species. However, the lack of up-to-date information about the spatial and temporal distribution of mesquite invasion has made the current control and monitoring methods unsuccessful. Consequently, detection and monitoring of Prosopis species is essential to provide reliable and accurate information about the spatial distribution and the level of invasive species dynamism into the native eco-community. This study investigates the ability of WorldView-2 imagery for mapping the invasion of P. glandulosa and coexistent indigenous species in the semi-arid region of Northern Cape Province, South Africa, using the random forest and support vector machines as classifiers. Our results show that the eight-band multispectral WV-2 imagery is able to detect and distinguish P. glandulosa effectively from the three coexisting indigenous species of acacia, with an overall accuracy of 86% at 2 m spatial resolution. This result shows that high-accuracy can be achieved with the multispectral WV-2 sensor. This high-accuracy provides the possibility for economically-feasible mapping of the distribution and spread of invasive alien plants and assists with the restoration and conservation process.

Aliens in the nursery: assessing the attitudes of nursery managers to invasive species regulations

The horticultural industry is recognised as a major pathway for the introduction and spread of invasive alien plants (IAPs). The Conservation of Agricultural Resources Act (CARA) of 1983 (Act No. 43 of 1983) listed and categorised invasive species with an aim to curb their spread. The more recently enacted Alien and Invasive Species Regulations under South Africa’s National Environmental Management: Biodiversity Act (NEMBA) are intended, in part, to improve controls on the horticultural industry’s role in the spread of IAPs. In order to assess, and enhance, the likely effectiveness of NEMBA, it is important to build an understanding of stakeholders’ awareness and attitudes towards the control of IAPs and associated regulatory policies. A two-pronged approach—involving nursery manager interviews (n = 30) and plant stock audit assessments (n = 41)—was used to gauge the awareness, compliance and attitudes of nursery managers towards both the CARA and NEMBA invasive species regulations. Less than ten percent of audited nurseries were fully compliant with the NEMBA regulations, and over 50% were stocking IAPs that have been regulated for at least 13 years under CARA. This is despite high levels of awareness (70%) about the CARA regulations reported in the interviews. The majority (73.5%) of IAP species stocked in nurseries were NEMBA category 1b invaders such as Nerium oleander and Canna indica. These are widespread and well-established invaders that require compulsory control under NEMBA. Half of the managers were not aware that the NEMBA regulations had been promulgated, but most respondents nevertheless reported being enthusiastic about compliance. Several factors were quoted as constraints on compliance by the industry. These included a perceived lack of enforcement, weak communication from government, and the lack of inclusion of the industry in the regulatory process. Suggested interventions that could enhance the impact of IAP regulations will involve improving the user-friendliness of the regulations, and supplementing the current top-down approach to regulation with an inclusive partner-centred approach.

Clearing invasive alien plants as a cost-effective strategy for water catchment management: The case of the Olifants river catchment, South Africa

Invasive alien plants have a negative impact on ecosystem goods and services derived from ecosystems. Consequently, the aggressive spread of invasive alien plants (IAPs) in the river catchments of South Africa is a major threat to, inter alia, water security. The Olifants River catchment is one such a catchment that is under pressure because of the high demand for water from mainly industrial sources and unsustainable land-use, which includes IAPs. This study considered the cost-effectiveness of clearing IAPs and compared these with the cost of a recently constructed dam. The methods used for data collection were semistructured interviews, site observation, desktop data analysis, and a literature review to assess the impact of IAPs on the catchment’s water supply. The outcomes of this study indicate that clearing invasive alien plants is a cost-effective intervention with a Unit Reference Value (URV) of R1.44/m3, which compares very favourably with that of the De Hoop dam, the URV for which is R2.93/m3. These results suggest that clearing invasive alien plants is a cost-effective way of catchment management, as the opportunity cost of not doing so (forfeiting water to the value of R2.93/m3) is higher than that of protecting the investment in the dam.

Alien flora of the Korean Peninsula

The Korean Peninsula has been divided into the countries of North and South Korea since 1948. This adoption of different political and socio-economic regimes has significantly changed economic activity and international exchange by those nations, thus affecting the introduction of alien plants. Our study objective was to provide a comprehensive, up-to-date inventory of the alien flora on the Korean Peninsula and to analyse how the partitioning between North and South Korea has influenced the numbers and status of those alien plants. We identified pre-1876 aliens that were brought to the Korean Peninsula before 1876, when Korea opened up to foreign countries, and also determined the post-1876 aliens that were introduced after 1876. Plants in the latter group were further classified into those that arrived before the outbreak of the Korean War in 1950 (1876–1950 aliens) and those introduced since then (post-1950 aliens). We investigated the regions of origin, family compositions, and invasion status of those alien taxa. In total, 504 alien taxa were identified, with 102 taxa being pre-1876 and 117 being 1876–1950 aliens. After the Korean War, the number of alien plants in South Korea more than doubled (276 taxa), whereas the number reported for North Korea was considerably lower (33 taxa). This might be due to enhanced economic activity and a larger human population in South Korea. Climatic differences as well as variations in the recording intensity for alien flora between North and South Korea may also have contributed to the large contrast in numbers of new alien species recorded during the last decades. Coordinated measures between the two nations are necessary if the spread of invasive alien plants onto the Korean Peninsula is to be reduced.

경주 동궁과 월지의 현존 식물상과 조경식재종의 분석

The purpose of this study is to offer raw data regarding landscape plantings of traditional cultural heritages by surveying and analysing the actual flora and landscape planting species distributed in Donggung Palace and Wolji Pond in Gyeongju, Korea. The results are as follows. The flora were summarized as 149 taxa including 65 families, 117 genera, 134 species, 1 subspecies, 10 varieties and 4 forms. The naturalized plants were of 18 taxa including Rumex crispus, Trifolium repens, Ailanthus altissima, Veronica persica, Senecio vulgaris, Festuca myuros and the like. Invasive species included Rumex acetosella. As a result of the analysis of chronological changes in landscape planting species, 23 taxa were planted in 1979, whereas 48 taxa were planted in 2014. Therefore, the number of these species increased by 25 taxa. The landscape planting species were of 48 taxa including 6 taxa of evergreen trees, 2 taxa of evergreen shrubs, 27 taxa of deciduous trees, 12 taxa of deciduous shrubs and 1 taxa of other. In present conditions by sections, Section A was 25 taxa, 15 taxa of Section B, 13 taxa of Section C and 29 taxa of Section D. The species planted in common were 4 taxa including Pinus densiflora, Acer palmatum, Euonymus alatus and Rhododendron yedoense for. poukhanense. The problems in the present conditions of landscape planting were volunteer species, the occurrence of scrub and vines and the spread of invasive alien plants. To restore and improve the planting landscape and facilitate tree growth, scrub, volunteer species and invasive alien plants must be removed.

Areas of high conservation value in Georgia: present and future threats by invasive alien plants

Georgia is known for its extraordinary rich biodiversity of plants, which may now be threatened due to the spread of invasive alien plants (IAP). We aimed to identify (1) the most prominent IAP out of 9 selected potentially invasive and harmful IAP by predicting their distribution under current and future climate conditions in Georgia as well as in its 43 Protected Areas, as a proxy for areas of high conservation value and (2) the Protected Areas most at risk due to these IAP. We used species distribution models based on 6 climate variables and then filtered the obtained distributions based on maps of soil and vegetation types, and on recorded occurrences, resulting into the predicted ecological distribution of the 9 IAP’sat a resolution of 1 km2. Our habitat suitability analysis showed that Ambrosia artemisiifolia, (24 and 40 %) Robinia pseudoacaia (14 and 19 %) and Ailanthus altissima (9 and 11 %) have the largest potential distribution (predicted % area covered), with A. altissima the potentially most increasing one over the next 50 years (from 9 to 13 % and from 11 to 25 %), for Georgia and the Protected Areas, respectively. Furthermore, our results indicate two areas in Georgia that are under specifically high threat, i.e. the area around Tbilisi and an area in the western part of Georgia (Adjara), both at lower altitudes. Our procedure to identify areas of high conservation value most at risk by IAP has been applied for the first time. It will help national authorities in prioritizing their measures to protect Georgia’s outstanding biodiversity from the negative impact of IAP.