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Invasive Alien Plants in the Azorean Protected Areas: Invasion Status and Mitigation Actions
Abstract
This chapter addresses plant invasions in the protected areas of the Azores (Northern Atlantic), whose flora encompasses a considerable proportion of alien species (about 70 %). The chapter includes (i) a general characterization of the Azores, with particular reference to their Island Natural Parks covering 24 % of the inland surface; (ii) an assessment of the plant invasion status of the Island Natural Parks (based on distribution data and expert evaluation of potential impacts and possibility of control of invasive alien plants); and (iii) a report about on-going and recent management initiatives embracing the control of invasive alien plants. The results show that the Island Natural Parks of Santa Maria Island is potentially the most threatened by invasive alien plants, followed in decreasing order by the Island Natural Parks of the islands of Graciosa, São Jorge, Corvo, Faial, São Miguel, Terceira, Flores and Pico. Some of the most threatening species are highlighted. Due to the innovative assessment methodology, the results do not fully corroborate previous studies, showing that just species listing may not provide a full understanding of the potential effects of invasive alien plants on native biodiversity, thus bringing new insights that may assist management initiatives. Several invasive alien plants management projects run by the Azorean Government and the Portuguese Society for the Study of Birds are described, with reference to those supported by the LIFE programme and PRECEFIAS (an Azorean project devoted to control of invasive alien plants in protected areas). Finally, a holistic discussion is provided stressing strengths and weaknesses of all topics covered in the chapter so that more effective invasive alien plant management strategies can be achieved in the future.
... In the Azores, the South African species Drosera aliciae and D. capensis have been introduced deliberately from cultivated material and since naturalized at some seepage habitats (Borges et al. 2010;Costa et al. 2013). In Brazil, plantings of D. capensis and D. binata into pristine CP habitats have fortunately been detected in time and could be removed completely (P. ...
Carnivorous plants and their unique habitats face various threats, most of them being an-thropogenic. About 25% of the known 860 carnivorous plant species are threatened or face extinction. Two of the threats are predominantly caused by "carnivorous plant lovers". The actions include 1) sale and trade of plants that have been illegally collected from the wild, a threat that has continuously increased in the past years and 2) planting of exotic carnivorous plant species into pristine habitats of native species. This article illustrates these problems and shows causal connections and the legal situation, which are apparently not known to everyone. A long-term solution can only be found if carnivorous plant lovers recognize and stop their misconduct. This article aims at closing knowledge gaps and to inform about the problem of threats to wild carnivorous plant populations by carnivorous plant lovers.
... and tree ferns, such as Sphaeropteris cooperi (F.Muell.) R.M.Tryon, Sphaeropteris medullaris Bernh and Dicksonia antarctica Labill., currently threaten the conservation of endemic Azorean species and natural forests (Silva and Smith 2006, Silva et al. 2009, Costa et al. 2013, Borges Silva et al. 2014, Borges Silva et al. 2017, Silva and Beech 2017, Borges Silva et al. 2018. ...
Background
The data presented here originated from field expeditions carried out between 2017 and 2018, within the framework of Forest-Eco2 project: "Towards an Ecological and Economic valorisation of the Azorean Forest". The project aimed to quantify the ecological value of the Azorean forests, including carbon accumulation and to design and propose measures that could further enhance forest sustainability. For that, 90 forest plots were sampled on three Azores islands - São Miguel, Terceira and Pico - equally distributed into natural forest, exotic woodland and production forest. The aim of this report is to further expand knowledge on biodiversity trends enclosed in the different forest types present in the Azores, by providing a list of the occurrences of the 105 different vascular plant taxa together with a brief characterisation of their origin and life-form.
... distribution remains nowadays [5]. In addition to further habitat destruction [6] and climate change [7], the current main threat to Laurel Forest, especially in the Azores, is invasive species that outcompete native Laurel Forest plant species, completely transforming the habitat and thus leading to the extinction of endemic species of different taxa [8][9][10]. ...
The Azores bullfinch (Pyrrhula murina Godman, 1866) is a rare Passeriformes endemic from the eastern part of São Miguel Island, Azores, Portugal. This bird was almost considered extinct in the first half of the 20th century, but due to recent conservation measures, it has experienced a recovery since the beginning of the 2000s. Despite the attention given to this bird, the size of its population is still controversial, and the most recent studies present significant divergences on this behalf. The purpose of the present study is to present data from the long-term monitoring and results of the third single-morning survey of the Azores bullfinch to update information about the population size and range of this species. In addition, we performed a literature review to highlight the limitations and advantages of the different approaches for monitoring this species. The Azores Bullfinch records during the single-morning survey indicated a reduction in the extent of occurrence and area of occupancy of this species in comparison with the previous studies, despite the increase in bird detection. However, we suggest that the distribution range of this species needs further analysis concerning its area to exclude non suitable habitats from this analysis. In this study, we conclude that the most likely size of the Azores bullfinch population is 500 to 800 couples, with a slow population growth tendency and an area of distribution of 136.5 km 2 .
... However, changes in land use have led to a drastic reduction in natural forest cover and the expansion of exotic woodland and production forest [45,46]. Besides land cover change, invasive species, including a large number of plant taxa that are recognized as problematic invaders worldwide, constitute a major threat to the preservation of the remaining natural plant communities in the Azores [47,48]. ...
Constructed wetlands are considered integrated ecosystems and a promising wastewater
treatment option, relying on vegetation, soils, and microbial assemblages. The potential dispersal of effluents from domestic septic systems, the application of dairy farm effluents containing excessive nutrients and pathogens into pastures, and undertreated effluent discharge in coastal areas are some of the threats to water quality in the Azores. Constructed wetlands could be used in the Azores to protect and preserve the quality of drinking water sources and bathing waters. However, the most used plant species in other regions are considered as introduced in the Azores, where a considerable number of invasive plants and weeds are already present. Here, we present a review of the plant taxa
already present in the Azorean flora with the potential to be used in constructed wetland systems, based on a literature review, and on the assessment of nine criteria. We evaluated 73 taxa, including mostly Cyperaceae, Poaceae and Juncaceae, showing that, although some of the top-ranking species were considered potentially noxious, several native and some naturalized taxa could be used for wastewater treatment. This work supports the implementation of constructed wetlands in the Azores, while minimizing the risk of new invasions.
... Furthermore, the Canary Islands, Madeira and Selvagens have provided examples of successful eradication and control schemes for rabbits, cats, mice, and plants (e.g., Bell, 2001;Olivera et al., 2010). In the Azores, a regional programme to control invasive alien plants in sensitive areas has revealed the importance of maintenance to prevent alien regrowth (Costa et al., 2013). ...
Research in Macaronesia has led to substantial advances in ecology, evolution and conservation biology. We review the scientific developments achieved in this region, and outline promising research avenues enhancing conservation. Some of these discoveries indicate that the Macaronesian flora and fauna are composed of rather young lineages, not Tertiary relicts, predominantly of European origin. Macaronesia also seems to be an important source region for back-colonisation of continental fringe regions on both sides of the Atlantic. This group of archipelagos (Azores, Madeira, Selvagens, Canary Islands, and Cabo Verde) has been crucial to learn about the particularities of macroecological patterns and interaction networks on islands, providing evidence for the development of the General Dynamic Model of oceanic island biogeography and subsequent updates. However, in addition to exceptionally high richness of endemic species, Macaronesia is also home to a growing number of threatened species, along with invasive alien plants and animals. Several innovative conservation and management actions are in place to protect its biodiversity from these and other drivers of global change. The Macaronesian Islands are a well-suited field of study for island ecology and evolution research, mostly due to its special geological layout with 40 islands grouped within five archipelagos differing in geological age, climate and isolation. A large amount of data is now available for several groups of organisms on and around many of these islands. However, continued efforts should be made toward compiling new information on their biodiversity, to pursue various fruitful research avenues and develop appropriate conservation management tools.
Small oceanic islands, such as São Miguel Island in the Azores (Portugal), face heightened susceptibility to the adverse impacts of climate change, biological invasions, and land cover changes, posing threats to biodiversity and ecosystem functions and services. Over the years, persistent conservation endeavors, notably those supported by the EU LIFE Programme since 2003, have played a pivotal role in alleviating biodiversity decline, particularly in the eastern region of São Miguel Island. This study advocates the application of remote sensing data and techniques to support the management and effective monitoring of LIFE Nature projects with land cover impacts. A land cover change detection approach utilizing Rao's Q diversity index identified and assessed changes from 2002 to 2021 in intervention areas. The study analyzed the changes in LIFE project areas using ASTER, Landsat 8, and Sentinel 2 data through Google Earth Engine on Google Colab (with Python). This methodological approach identified and assessed land cover changes in project intervention areas within defined timelines. This technological integration enhances the potential of remote sensing for near-real-time monitoring of conservation projects, making it possible to assess their land cover impacts and intervention achievements.
The removal of invasive species and mitigation of habitat loss are vital conservation tools for species such as seabirds. We surveyed habitats across the entirety of a small seabird islet reserve, Ilhéu da Praia, in the Azores, two decades on from mammalian eradication and floral restoration. Here, we present a fine-scale map, to a 12 metre resolution, representing the first full habitat survey of this islet. This resource can serve as a baseline for monitoring future habitat changes to this internationally important seabird islet. Following restoration efforts in the 1990s, the islet's dominant habitats are meadow, grassland dominated by Festuca petraea, or a combination of the two. We also report a novel observation of both Band-rumped Hydrobates castro and Monteiro's H. monteiroi Storm Petrels breeding in the cavities of Tamarix africana, an invasive tree species. Published in Seabird.
Freshwater systems on remote oceanic islands are particularly vulnerable to biological invasions. The case of freshwater ecosystems in the Azores Archipelago is especially relevant considering the islands’ youth and remoteness, and low natural connectivity. This study presents a review of the introduction and presence of non-indigenous freshwater species in the Azores, retrieved from various historical records, paleoenvironmental reconstructions, published records, and field data from two decades of the Water Framework Directive (WFD) monitoring programs. At least 132 non-indigenous freshwater species have successfully established in the Azores, belonging to several taxonomic groups: cyanobacteria (10), synurophytes (1), desmids (1), diatoms (20), plants (41), invertebrates (45), amphibia (2), and fishes (12). Intentional and accidental introductions have been occurring since the establishment of the first human settlers on the archipelago, impacting freshwater ecosystems. The first reported introductions in the Azores were intentional fish stocking in some lakes. Non-deliberate introductions have recently increased through transport-contaminants (51%) associated with the aquarium trade or agricultural products. In the Azores, the highest number of non-indigenous species occur on the largest and most populated island, São Miguel Island (116), followed by Flores (68). Plants constitute the most representative group of introduced species on all islands, but invertebrates, diatoms, and fishes are also well established on most islands. Among invertebrates, non-indigenous arthropods are the most well-established group on all islands except on the smallest Corvo Island. Many non-indigenous species will likely benefit from climate change and magnified by globalization that increases the probability of the movement of tropical and subtropical species to the Azores. Present trends in international trade, importations, and enhanced connectivity of the archipelago by increasing flights and shipping will probably promote the arrival of new species. Augmented connectivity among islands is likely to improve non-indigenous species dispersal within the archipelago as accidental transportation seems to be an essential pathway for non-indigenous freshwater species already present in the Azores.
Tourists have become increasingly interested in certain aspects of their destination, including landscape and biodiversity elements, thereby promoting the development of nature-based tourism. The Azores are considered a sustainable tourism destination, with various natural attractions, including hiking trails. Based on the hypothesis that natural vegetation/forest might have a relevant role as a tourist attraction along trails, we performed a quantitative GIS-based analysis to determine the predominant types of land cover found along hiking trails in the Azores. Different statistical approaches indicated that agriculture/pastureland dominated land cover along most trails and that land cover distribution was correlated with global land cover partitioning in the respective island. A reduced number of trails showed a distinct land cover, intersecting areas of natural vegetation/forest. Therefore, we concluded that land cover across hiking trails in this nature tourism destination was dominated by a humanized landscape, which raises questions regarding the more adequate tourist interpretation strategy to adopt in the Azores.
Recent studies have shown that Macaronesia has considerable problems with exotic species, particularly those considered as invasive. For instance, in the Azores more than 60% of the vascular plant flora consists of non-indigenous species (Silva & Smith 2004, 2006). Several plants are presently considered to be serious threats not only to the conservation of the Azorean endemic flora and native plant communities, but also to the conservation of bird species, namely the Azores bullfinch (Pyrrhula murina) and of arthropods (Borges et al. 2006). In Madeira Archipelago, species like the black rat (Rattus rattus) and the domestic cat (Felis silvestris catus) are known to have a strong negative impact on populations of native birds. In the Canaries, about 11% of the terrestrial biota corresponds to alien species, and some recent introductions originated some social alarm, namely the recent naturalization of a species of snake (Lampropeltis getula) in Gran Canaria.
However, of the considerable number of introduced species, how many are considered
as really invasive (i.e. they are not only naturalized but are presently causing a negative
impact on the Macaronesian biota)? Among those species, which are amenable to control or eradication? Which species should be considered priorities for control actions and other measures because they are causing impact but are still possible to control or eradicate?
For instance, in Canaries the Barbary ground squirrel (Atlantoxerus getulus) is
considered an emblematic invasive alien species (IAS), but is it the top-ranking invader in
Macaronesia? French Hydrangea (Hydrangea macrophylla) is a touristic icon in the Azores, but is now also considered as an invasive alien species. What is the real impact of the different species of alien rodents in Macaronesia?
Although negative impacts have been a concern, should positive impacts also be considered? For example, several alien species still have and will most probably continue
to have an important role in the islands’ economy or as game species.
This book aims to answer some of these questions. It is a first attempt to present
information regarding alien species in the European region of Macaronesia in a systematic way. Undoubtedly, this is a difficult task, due to differences regarding legislation but also to the differences in the general treatment given to IAS in the different archipelagos.
A standard set of criteria was designed and applied to those species considered as
naturalized and occupying natural and semi-natural habitats. A first set of criteria was
used to score the effect on biodiversity values, in terms of species and habitats, which are
being affected by the invasive species. A second set of criteria was used to score the
feasibility of control or eradication of the invasive species. In this second set of criteria we
also included items reflecting the social importance of the species concerned. The
application of both sets of criteria has allowed identification of the most noxious IAS in
Macaronesia and also the ranking of those species according to a management priority.
This is of considerable importance, since, due to the large scale of the IAS problem not
only in Macaronesia but globally, it is not possible to control every introduced species.
Resources will have to be allocated to those species that are still possible to control or
eradicate with sustainable costs. Although the criteria were applied by experts from each
archipelago, a global Macaronesian approach was possible after a thorough analysis and
careful treatment of the data from each archipelago, this being the main objective of the
book.
This book is also intended to serve as a tool to raise awareness of the problem of IAS.
In fact, island ecosystems have been considered as more susceptible to IAS than
continental systems, largely due to the small scale of the islands and to peculiarities of
island biota which make them more susceptible to foreign competitors, predators and
pathogens. However, islands, particularly European islands, are important hotspots for
biodiversity, and the preservation of this natural heritage is currently also dependent on
the implementation of effective measures to contain IAS
1. The Azores bullfinch (or Priolo), Pyrrhula murina, is largely confined to native forest in the east of the island of S. Miguel (Azores). This paper assesses the impact of a recent large-scale invasion of the native forest by exotic flora on the population and distribution of this species. It examines the population size and importance of vegetation characteristics to explain the seasonal distribution of this bird. The conservation of this population, including the planning of forest management practices is addressed. 2. Point-counts and capture-recapture indicate a population of 60-200 pairs. The bird occurred all year round in the largest fragment of native vegetation to the east of the range and was recorded in a smaller patch to the west only in autumn. 3. The Azores bullfinch's monthly density was much higher in laurel forest than in exotic forests (Cryptomeria japonica and Pittosporum undulatum). There were peaks in the density of birds in exotic forests in summer and autumn. The edge of the native forest was important from May to December and the interior from January to April. The degree and intensity of the selection of habitat structure varied seasonally. More habitats were selected over summer than over winter. Native forest and Clethra arborea were highly preferred at all seasons. Bare ground and short vegetation were selected in summer and avoided in winter. 4. The Azores bullfinch was sedentary but ranged widely locally. They appeared more mobile over summer than over winter. Larger-scale altitudinal movements were carried out in May. 5. Monthly habitat selection may be interpreted as preference for habitats where feeding resources are more abundant. A large home range is needed in summer because birds feed in openings that are separated by unsuitable tall vegetation. 6. Both demographic and environmental stochasticity are important factors in the conservation of the small population of Azores bulfinch. The first factor may not be the major one because the population may have increased recently due to the introduction of C. arborea and also because recruitment seems to compensate annual adult mortality. The invasion of the native forest by aggressive exotic flora seems to be the most important environmental stochasticity factor affecting this population. Present exotic forests are too dense but they could be valuable habitats in summer if they were more scattered. Improvement of the habitat quality of the existing native forest and expansion of its area are important nature conservation strategies for this population.