A silent invasion threatening European cities

The story of a rabbit population deep burrowing in a graveyard area, loosening the roots of trees, making tombstones fall, and horrifying people, may look like the plot of an old B horror movie. Yet, this is what the experts reported about the situation in Helsinki, where in 1985 rabbits established a feral population descended from pets dumped in the wild. Outside their natural range (the rabbit is native to the southern Iberian Peninsula), this species is considered as a key driver of ecosystem change, as it can cause extensive erosion of soils by overgrazing and burrowing which in turn can cause significant impact on the composition and local abundance of native wildlife. The impacts caused by this species can be very severe, also causing terms of economic losses. For example, until now the estimated economic impact of rabbit in Helsinki exceeds € 2 million. 

Feral rabbit © Photo: Riccardo Scalera

The rabbit is only one of the many alien species introduced in urban environments and whose impact is discussed in the new IUCN report “Invasive alien species: the urban dimension”. The IUCN report includes 26 case studies aimed at providing insights on problems, challenges, actions, approaches, human and financial resources, and lessons learnt, for a selection of species and countries. In fact the report was produced and released as a key output of the conference “Invasive alien species: the urban dimension” which will take place on 5 September at IUCN Headquarters, Switzerland. The objective of the conference is to emphasize the role of municipalities in the management of invasive alien species in urban environments, and more importantly, to highlight the importance of their contribution to the implementation of the new EU legislation for invasive alien species, which should finally be released in early September 2013. For more details and updated information on the conference and the upcoming EU legislation see here.

As shown by the many contributions published in the new IUCN report, urban environments – often characterised by high levels of disturbance, high intensity of transport, and high environmental heterogeneity - have usually played a crucial role in biological invasions. This is also due to the fact that within urban environments a number of potential entry points and pathways concentrate, such as botanical gardens and zoos, along with nurseries and private gardens. Besides, urban areas are privileged centres for some of the most prominent pathways and vectors, including trade of pets, ornamental plants, etc. which can increase the propagule pressure that facilitates the invasion processes. Not surprisingly, many studies have demonstrated that cities are hotspots of invasions, particularly for plants. Human settlements are often the point of origin of many invasive species, that from these areas then spread into adjacent landscapes along transport corridors such as railways, waterways and roads, in many cases eventually arriving to invade natural areas.

Drawing © Riccardo Scalera

It is clear that urban environments can play a much wider and important role in addressing the risks of biological invasions, e.g. for making citizens aware of the importance of biodiversity, and promoting the implementation of dedicated actions among the competent administrations. For example, many institutions usually based in towns, such as botanical gardens, zoos, aquaria, university departments, natural history museums, conservation agencies and institutions, can be key players in global conservation programmes, by and attracting and leveraging hundreds of millions citizens, thus contributing to public outreach and raising awareness. Many such institutions might offer unique opportunities for dedicated environmental education programmes, thus could contribute significantly to raising awareness to prevent the introduction of new invasive alien species (e.g. through specific information activities targeting the general public or specific stakeholders). Finally, as shown by the reported case study, local administrations can be players of fundamental importance for the successful implementation of conservation related activities, i.e. from research projects to eradication/control initiatives. 

Alarm for invasive hornet rapidly expanding European range

It was easy to predict the arrive of the Asian hornet in Italy. This invasive alien species native to South-East Asia, was recorded in Europe for the first time in France in 2004, where it was probably introduced accidentally through the horticultural trade. It spread very rapidly across south-western France (at around 100 km per year), and soon reached Spain, Portugal and Belgium. At the time the EEA report on invasive alien species impact was published (December 2012) it was considered likely to arrive soon also in Italy and Great Britain. In fact the news of the arrive of this hornet in Italy was circulated in May 2013, although the new record of the species originates from monitoring activities carried out already in November 2012 (see press release of the University of Turin). This shows that an effective early warning and rapid response system for alien species in Europe is urgently needed, so as to prevent further impacts related to biological invasions.

The Asian hornet © Photo courtesy of Quentin Rome

Invasion risk modelling already suggested that the Asian hornet - Vespa velutina or yellow-legged hornet to be more precise - could spread over a large part of Europe (see article published on Aliens no.31). And there are good reasons to be concerned about the spread of this “giant wasp”. With a body length of 2-3 cm Vespa velutina is in fact a social wasp slightly smaller than the native European hornet Vespa crabro. The head is black with an orange-yellow face. The body is dark brown or black velvety, bordered with a fine yellow band and a single abdominal segment almost entirely yellowy-orange, which makes it difficult to confuse with any other species.

The Asian hornet and its nest © Photo courtesy of Quentin Rome

The Asian hornet is mainly a predator of social wasps and bees, and like the European hornet, it also consumes a wide variety of other insect preys. Honeybees are among the hornet’s main preys, so the Asian hornet is expected to have an economic impact on beekeeping activities. In fact, as a highly effective predator, the new hornet may represent an additional component to the decline of honey bee populations in Europe and its big colonies and diet spectrum suggest that it could have a noticeable impact on biodiversity, including many wild pollinators and other beneficial insects. Otherwise, this species is no more dangerous for humans than the European hornet as in general it is not aggressive. However, its large size, painful sting and noisy flight make it a very frightening insect (and stings may potentially cause life threatening allergic reactions). In general, they will not attack as long as the colonies remain undisturbed, so it is necessary to avoid getting close to their very large nests, which are from 50 to 80 cm in diameter, and might be found in tall trees in urban and rural areas, including garages, sheds, and sometime in holes in walls or in the ground.

The life-cycle of this social insect is very efficient: each colony, initiated by a single individual, can produce several thousands of workers, plus hundreds of males and new founders able to mate and subsequently produce new colonies. Nevertheless research to develop an effective control method for Asian hornets is still in progress. You can find additional information about the species and the relevant management options, as well as the contact details for expert assistance on this link.

Marine mammals on their way to new seas

White whales and grey seals have found a new home in the Black sea. In fact one of the largest organism introduced by humans  outside its natural range is the beluga. This beautiful marine mammal, not to be confused with the homonymous European sturgeon, is also known as white whale (the word beluga derives from white, in Russian). It should be remarked that the name is a bit misleading, as the beluga is a toothed cetacean and as such is rather a dolphin than a whale. Like other dolphins, belugas have been introduced in the Black Sea as a consequence of escapes and/or releases from coastal dolphinaria and oceanaria (where animals are kept in near-shore open-air pens which do not adequately prevent escapes of captive animals into the sea - see also a previous article here). The story of the beluga whale in the Black Sea started in the early 1990s, when one individual captured in Sakhalin Bay, Russia, was transferred to Crimea, Ukraine, where it was immediately released, or escaped, into the sea (actually, it was recaptured once, and then soon after released/escaped again). Another beluga was indeed released (or escaped) at the same time and place, and was also observed and reported in the wild several times. The two beluga whales were often observed in the wild near the Turkish, Romanian, Bulgarian and Ukrainian coasts, but their current status is unknown (more details on Birkun 2002; Reeves & Notarbartolo di Sciara 2006).

Interestingly the list of marine mammals spontaneously released in the Black Sea includes also other species, like the grey seal, the northern fur seal, the Steller sea lion, the harbour seal, the Caspian seal and, possibly, some other pinnipeds. Such cases of escape/release have been known in the Black Sea since the early 1980s, but occurred also in other regions. For example, the escape of a sea lion from an aquarium to the wild is also known in the Canary Islands. Otherwise three sea lions escaped from the Prague zoo after the severe flood of 2002, they were all recaptured within a few days, but one of them managed to roam for hundreds of kilometers along the Elbe river from Prague to Dresden, before being recaptured.

Harbour seals at Copenhagen zoo ©  Photo: Vibe Kjaedegaard

The number of animals escaped and/or released in the Black Sea is unknown (but is likely around a few tens), and also the actual fate and impact of the relevant species is uncertain. It is likely that the marine mammals escaped from dolphinaria and similar facilities did never lead to established populations, however it is known that species may have a very long lag phase before getting naturalised, or showing any impact. Of course this does not mean that in the meantime they do not affect the hosting ecosystem. This is especially true in the case of long-living organisms, in which case also a single animal can have a major impact on the ecosystem. For example there is some concern that they could be a source of infections circulating in dolphinaria. In any case such introductions show that the extent of the problem can be unexpectedly large, both in terms of size of animals moved from place to place, and in terms of size of ecosystem affected.

On the other hand, a recent paper by Gladilina & colleagues (2013) highlighted some positive aspect related to the introduction of an exotic grey seal in the Black Sea. The presence of this North Atlantic species has been regularly recorded in the north-east Black Sea since 2001. Its introduction is considered the consequence of an escape from captivity. Surprisingly, no major conflicts have been recorded with fisheries, as fishermen seem to tolerate the presence of this mammal despite the little damage to fishing gears. In any case, the seal seems perfectly adapted to the new environment. This led Gladilina and colleagues to assume that the long term survival of the grey seal in the Black Sea might indicate the possibility of successful re-colonization of the area by monk seals, the only extant aboriginal pinniped in the Black Sea, disappeared at the end of the 20th Century. Hopefully this will be compatible with the growing "novel" community of marine mammals.

Always look on the bright side of LIFE!

Up to € 278 million are available to EU Member States for projects under the seventh LIFE+ call for proposals recently published, and also this year invasive alien species (IAS) are explicitly mentioned within the “Indicative list of themes for LIFE+ Nature and Biodiversity projects”. This means that biological invasions are one of the themes for which the European Commission (EC) would welcome receiving proposals to be co-financed. In fact, two headings are particularly suitable for addressing the problems of IAS: Nature and Biodiversity (NAT) and Information and Communication (INF). For example, according to the NAT application brochure:

 Within the classic LIFE+ Nature projects most of the priorities listed in the EU Biodiversity Strategy to 2020 may be effectively addressed: e.g. invasive alien species through control and eradication in and around Natura 2000 sites

The LIFE brochure on IAS

Under the NAT heading, two different strands exist, which are characterized by different requirements and approaches. Under the LIFE+ Nature strand, it is possible to submit projects for the control and eradication of IAS affecting either the Natura 2000 network or species covered by the Habitats and Birds Directives. Site-related conservation measures for combating IAS can be planned both inside Natura 2000 sites (insofar as they are not recurring actions and they directly benefit the species/habitats targeted by the project) and outside Natura 2000 sites. In the latter case, such measures should be carried out  on strategic spots near or adjacent to a Natura 2000 site to improve the conservation status of the species/habitats target, and to limit or prevent damage within the site. In case of species-related conservation actions for combating IAS (that are not site-related), they can be eligible insofar as they directly benefit the species of the Birds and/or Habitats Directives targeted by the project. Some special requirements must be considered in such a case. For example, applicants must provide guarantees and commitments that the investments made will be sustained in the long-term. The explanatory notes of pag.53 of the application brochure provide some additional indications on the requirements for the range of actions that can be envisaged, e.g. prevention of introductions through the prioritisation and management of pathways, establishment of early warning and rapid eradication system, and management of established IAS. The important is to show solid scientific evidence regarding the added value of the foreseen actions for the Natura 2000 sites/network, and to include an awareness raising component, particularly towards stakeholders involved in the introduction of IAS.

In case of projects aiming at tackling IAS not necessarily in respect to the Natura 2000 network, it is possible to consider submit proposals under the LIFE+ Biodiversity strand, in which case they must have a clear innovative/demonstrative character. For this particular strand, the application brochure welcomes 

projects addressing the threats posed by IAS (1) by preventing the introduction of invasive alien species, in particular by tackling pathways of unintentional introduction, (2) by establishing an early warning and rapid response system and (3) by eradicating or controlling established invasive alien species (in line with the dedicated legislative instrument which is currently under preparation, see here). 

Also in this case, the explanatory notes of pag.57 of the application brochure provide some useful clarification. In fact, also such proposals should include an awareness raising component, in particular towards stakeholders involved in the potential introduction of IAS, and should have measurable biodiversity benefits as one of their main outcomes. Besides, the foreseen actions should be targeted towards the achievement of the 2020 Biodiversity Strategy.

It is also possible to present projects dealing with the IAS issue within the INF heading. In relation to this Information and Communication strand, it is worth mentioning that the LIFE+ programme has developed a logical framework useful to design an effective communication campaign, likely to achieve some measurable impact on the environmental problem targeted (e.g. the impact of IAS) and on the level of awareness (about IAS and their threat), by addressing a specific target audience and gaining the support of specific stakeholders, and by monitoring such impact through specific indicators. More details are included in the LIFE+ INF 2013 Application Guide.

The invasion of the allergenic ragweed in Europe

The common ragweed is one of the most pollen-allergenic plants and as such represents a serious health risk for humans. Its pollen is a potent trigger of hay fever, rhinoconjunctivitis, and may often cause severe asthma-like symptoms. In Europe the incidence of ragweed allergy ranges widely from 2-50% of the allergic population (roughly ¼ of the European population shows general allergic rhinitis). The impact of common ragweed on human health – affecting mostly children and urban populations (but also horses, dogs and cats) - is not restricted to areas invaded by the plant. In fact, due to transport of ragweed pollen by air masses, allergy reactions are recorded in distances of 100s of km from the site where the plant is situated. Besides, the common ragweed also contains volatile oils that may cause skin irritation and hypersensitivity dermatitis. The associated economic costs are estimated to be around 4.5 billions of euro per year. In addition to this, the ragweed can also have an harmful impact on other sectors, such as agriculture (depending on infestation levels and success of control, yield losses of over 50% are reported). 

A synthetic and systematic review of all available information on the current extent of ragweed infestation in Europe has just been published by the EU within the new comprehensive report “Assessing and controlling the spread and the effects of common ragweed in Europe”.  The study, carried out by an international team of experts led by the Natural Environment Research Council (UK), includes an economic, social and environmental quantification of direct and indirect harmful effects in all sectors, as well as an assessment of measures to control ragweed spread and introduction (now and in future climates). 

Common ragweed (male flowers) ©  Photo: Daniela Bouvet

The common ragweed is actually a native to North America, which has colonised several countries around the world – e.g. Europe, as well as parts of Australia, China, Japan, South America and Taiwan – mostly as a contaminant of agricultural products (including the grain mixtures used as food for birds), machinery or construction materials. In Europe, where it was first introduced in France and Germany in the 1860s, started its spread in the entire region some 20-25 years ago. The result is that large populations of ragweed are now present in the old continent, particularly in Croatia, France, Hungary and Italy, but the distribution range is still expanding as a consequence of changing climate and perhaps adaptation to local climate. Moreover, changes in agricultural land use with large-scale set-aside and abandonment practices, along with an increase of the construction sites and wasteland, are expected to provide new suitable habitats for ragweed. 

The key successful features of this annual herbaceous plant - which can reach a height of over 2 m - are its great adaptability to hostile habitats, its strong ability for re-growth after mowing, and the capability of seeds to remain viable for up to 35 years in soil seed banks. It is most frequently associated with agriculture and is found in cultivated fields (mainly maize, sunflower, leguminous plants) and along irrigation canals. This typical pioneer species is also associated with frequent and extensive disturbance regimes resulting from other human activities (e.g. riverbanks, roadsides, railways, gravel pits, construction sites, waste sites, urban areas, building yards, private gardens and parks).

Common ragweed (leaves) ©  Photo: Daniela Bouvet

The common ragweed is now so widespread in Europe that eradication at this stage of the invasion is no longer feasible. However, it is possible to keep the ragweed under control by every year eliminating emerging plants as far as possible, and preventing or reducing the spread of seeds from infested to non-infested sites. So far, no successful biological control methods have been developed, thus the most effective management measures to control the propagation of this plant are clipping/mowing, uprooting, ploughing, mulching and chemical treatment. Preventive measures include initiatives to limit unintentional spread of ragweed seeds by developing and implementing best practices. In this context, a well‐targeted intensive awareness raising campaign is a key to success of both prevention and control strategies (e.g. by reporting observations and making early detection possible). In fact, the EU study has shown some promising future scenario: while in 20 years time the overall impact is expected to slightly increase (about 3%), the implementation of sound management strategies could help reducing such impact by approximately 50%.