Tag: invasion ecology

Experiment suggests the best ways to tackle invasive Oregon grape in Belgian coastal dunes

The Belgian coastal dunes, a protected habitat of high conservation value, are getting severely impacted by one of its worst enemies amongst invasive species: the Oregon grape. To help mitigate the detrimental effect of this North American shrub invader, Belgian scientists carried out an experiment to assess the effectiveness of different management methods.

The Belgian coastal dunes, a protected habitat of high conservation value, are getting severely impacted by one of its worst enemies amongst invasive species: the Oregon grape. To help mitigate the detrimental effect of this North American shrub invader, Belgian scientists carried out an experiment to assess the effectiveness of different management methods.

The Atlantic coastal dunes form a dynamic and diverse ecosystem, home to a large number of native species, many of which are regionally threatened. Embryonic dunes, shifting white dunes, moss dunes, dune grasslands, and dune slacks are considered high conservation value sites, according to the interpretation manual of European habitats. However, the dunes are highly affected by external influences, and one of the most important threats to their biodiversity are invasive non-native plant species. These plants often colonised the dunes as garden escapes or spread from garden waste dumps or public plantings. Oregon grape is one of the worst invaders amongst them.

Oregon grape growing on sand dune (Belgium).
Photo by Tim Adriaens.

In their study, published in the open-access journal NeoBiota, the scientists, led by Tim Adriaens and Sam Provoost of the Research Institute for Nature and Forest (INBO), focus on the management of the current populations of Oregon grape (Berberis aquifolium) in the Belgian coastal dunes, where the species has already managed to invade half of the 46 nature reserves and is starting to replace native vegetation. Such a negative effect on the biodiversity of the area requires practical management advice. Due to the high level of infestation of the dunes, the researchers recommend prompt eradication as the most appropriate management strategy. So far, however, it has been unclear which method would show the best effectiveness.

“Invasive shrub species exert an additional pressure on Belgian dune ecosystems, which are already highly fragmented by urbanisation. Oregon grape is one of the worst and should be tackled urgently before it gets out of control,” says Tim Adriaens.

Having compared four previously suggested treatments: manual uprooting, foliar herbicide application, stem cutting followed by herbicide and salt application, the scientists reported herbicide leaf treatment to be the most effective method. Manual removal by digging and treating stems with glyphosate showed medium effectiveness. Treating stems with a saturated salt solution appeared rather cosmetic. However, it’s not that easy to choose which method would be the best to work with, since with herbicide use there are non-target effects on the environment, economy, and society to be considered.

Dune restoration by mechanical removal of dense Oregon grape infestation (left) and leaf treatment of Oregon grape clone with a hand sprayer (right).
Photo by Tim Adriaens.

“Individual clones are best treated with herbicide, large surface areas provide opportunities for landscape-scale ecological restoration, combining invasive shrub removal with sand dune creation,” further explains Tim Adriaens.

In Belgium, Oregon grape was first recorded in the wild in 1906 and naturalised in the period 1920-1950. It has been spreading rapidly since the 1990s. This expansion might be linked to cultivated hybrids and global warming, with the latter leading to a lengthened growing season, suggest the scientists. The species likes calcareous soils. Along the Belgian coast, Oregon grape has mainly invaded grey dunes, scrub and woodland.

Thanks to its numerous blue berries, which are easily dispersed over long distances by songbirds, the plant can appear everywhere within the dunes sites, also in places hardly accessible to managers. With the help of a highly branched root system, the plants attach themselves firmly in the sand, which makes manual pulling of mature plants hardly possible and labor-intensive.

“Dune managers and scientists across Europe should unite to draft alert lists and prioritise established alien species for management,” Tim says in conclusion.

In conclusion, the scientists highlight the importance of an EU-wide collaboration between scientific communities. Invasive species are not bothered by administrative borders and exchanging experiences on impact and management options is crucial to maintain dune ecosystems in good conservation status.

Coastal dunes in Belgium provide unique habitat to many Red listed species.
Photo by Tim Adriaens.

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Original source

Adriaens T, Verschelde P, Cartuyvels E, D’hondt B, Vercruysse E, van Gompel W, Dewulf E, Provoost S (2019) A preliminary field trial to compare control techniques for invasive Berberis aquifolium in Belgian coastal dunes. NeoBiota 53: 41-60. https://doi.org/10.3897/neobiota.53.38183

Invasive parrots have varying impacts on European biodiversity, citizens and economy

The monk parakeet (Myiopsitta monachus), also known as the Quaker parrot, is another South American species, known from the temperate to subtropical regions of Argentina and neighboring countries.
Photo by ParrotNet.

Non-native parrots can cause substantial agricultural damage and threaten native biodiversity, although impacts vary strongly depending on where these parrots have been introduced. Brought to Europe as pets, escaped or released parrots have established numerous wild populations across Europe. Tens of thousands of ring-necked and monk parakeets make up the bulk of Europe’s parrots, but several more species are gaining a foothold too.

A pan-European team of researchers, conservationists, wildlife managers and policy-makers worked together under the umbrella of ParrotNet, an EU COST Action, and have reviewed the available evidence on parrot damage, concluding that measures to prevent parrots from invading new areas are paramount for limiting future harm. Their findings are published in the open-access journal NeoBiota.

The ring-necked parakeet (Psittacula krameri), also known as the rose-ringed parakeet, originates in Africa and South Asia.
Photo by ParrotNet.

Introduced parrots can damage the environment, but severe impacts remain rare and localised. So far, most reports of damage are linked to the widespread and locally abundant ring-necked and monk parakeets. Studies show that in their native ranges, both species can and regularly do inflict large crop losses, but in Europe, expectations of comparable widespread and severe damage to agriculture have so far failed to materialise.

In Europe, competition with native species presents a more serious problem, especially for ring-necked parakeets as they can compete with native species for food and breeding sites. Meanwhile, in the Americas, monk parakeets are notorious for the damage their stick nests cause to power infrastructures by catching fire, yet very little evidence for such problems exist in Europe.

Reported impacts for other parakeet species in Europe are virtually nonexistent, probably because these species have been introduced more recently and currently exist as relatively small and localised populations.

Dr Diederik Strubbe of the Terrestrial Ecology Unit, Ghent University (Belgium) elaborates:

“It was already well known that introduced parakeets can cause damage. There is the oft-cited example of a vineyard in Surrey (UK) where ring-necked parakeets caused a loss of thousands of bottles of wine. In Seville (Spain), the same parakeet species is threatening an endangered native bat population by evicting them from their roosting tree cavities. Our review of all reported impacts however shows that such severe damage is not the norm. In most cases, parakeets introduced to Europe only do limited damage and, for example, about half of the studies focusing on competition between introduced parakeets and native species explicitly report no evidence of impact.”

The study also highlights that differences in the type of damage, and the way they are reported and summarised influences the outcomes of invasive species impact assessments.

The generalised threat level that invasive species pose is often based on their worst known impacts, whilst the capabilities of a species to do damage often requires specific circumstances. While this is relevant information for identifying those invaders that can potentially have major impacts, it is not necessarily representative of the impacts the species is likely to have when introduced to a new area. Similarly, including damage reports from the native range or from other invaded ranges typically results in higher threat level estimates compared to what actually has been observed in Europe.

What can be done to mitigate parakeet impacts?

The Alexandrine parakeet (Psittacula eupatria), also known as the Alexandrine parrot, occupies a natural range that extends from Afghanistan to Vietnam, including all of India, Sri Lanka and the Andaman Islands.
Photo by ParrotNet.

Based on the results of the study, the ParrotNet members also published a ‘policy brief’, summarising and discussing the implications of their findings for policy makers and wildlife managers. Their recommendations include stricter regulation aimed at preventing parakeet introductions, rapid response when emerging populations are detected and better dissemination of information to the public about the impact parakeets can have. For example, using bird feeders that parakeets cannot access may help reduce the abundance of these birds in cities.

Prof. Jim Groombridge of the Durrell Institute of Conservation and Ecology (DICE), School of Anthropology and Conservation, University of Kent (UK) comments:

“What should be done to minimise damage by invasive parakeets is ultimately up to policy-makers. But as scientists, we stress that our work again highlights that the best way to combat invasive species is to prevent their introduction and spread. Parakeet populations have already been successfully removed, for example, from islands such as the Seychelles, demonstrating that it is possible to stop them when prompt and decisive action is taken by governments. For the already established and large parakeet populations that can be found across parts of Europe, there is no ‘silver bullet’ solution to the problems they may locally pose. More applied research is needed to find cost-effective and acceptable methods to reduce parakeet impacts in those areas where they do cause damage”.

The nanday parakeet (Aratinga nenday), also known as the black-hooded parakeet, is a species native to South America.
Photo by ParrotNet.

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Original source:

White RL, Strubbe D, Dallimer M, Davies ZG, Davis AJS, Edelaar P, Groombridge J, Jackson HA, Menchetti M, Mori E, Nikolov BP, Pârâu LG, Pečnikar ZF, Pett TJ, Reino L, Tollington S, Turbé A, Shwartz A (2019) Assessing the ecological and societal impacts of alien parrots in Europe using a transparent and inclusive evidence-mapping scheme. NeoBiota 48: 45-69. https://doi.org/10.3897/neobiota.48.34222

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The ParrotNet Policy Brief can be downloaded from: https://www.kent.ac.uk/parrotnet/policybrief/.