Temporary habitats within multifunctional agriculture for the water shrew (Neomys fodiens) and tree frog (Hyla arborea) in the Baakse Beek study area Coen Westerduin Plant Production Systems Group, Wageningen University, Wageningen, the Netherlands Various factors have contributed to the decline of many organisms, including the Eurasian water shrew Neomys fodiens and the European tree frog Hyla arborea, over the past decades. This literature study focuses on the habitat requirements for these two animals, including water quality, food and vegetation, to investigate a re-introduction of these species in the Baakse Beek area in the east of the Netherlands, which is one of the subjects of study of the CARE (Climate Adaptation for Rural arEas) project. Developmental possibilities and timescales are investigated to find out if only temporary living areas for these animals could be accomplished, allowing for freedom of land use for farmers in the area. The varied diet, tolerance to pollution, relative independence of vegetation and lack of preference for different substrates or banks, complemented by its little affinity to certain areas and short lifespan, seem to make N. fodiens a suitable candidate for such schemes. Higher demands for water quality by H. arborea are the main objections against introduction of this species in an eutrophicated agricultural landscape. Dependence on vegetation and a habit of returning to older, no longer existing habitats provide further arguments against this practice. However, more research is needed on the optimum habitats of both animals, as reasons for their decline, and as such their requirements, are still ill- understood. 1. Introduction agricultural area in the Netherlands was involved Habitat loss, pollution and several other factors in nature conservation, well below the EU have resulted in a decline or even local extinction average of 25% in 2002 (Berentsen et al., 2007). of many plants and animals worldwide. For some Various inquiries have been carried out to find of these, conservation alone will not be enough to what motivated farmers to participate in forms of sustain them, but restoration and construction of nature conservation, or deterred them from doing suitable environments is necessary. so. Berentsen et al. (2007) found financial benefits As a country lacking large areas of nature, such to be the most important reason to participate, policies in the Netherlands often rely on and subsidies should increase to cover the participation from the agricultural sector. In agri- conservation costs. Governmental interference environmental schemes (AES), farmers are paid to should also be kept to a minimum, as this made modify their farming practise to provide farmers feel they were not in charge of their own environmental benefits (Kleijn and Sutherland, business. Extensive research by Jongeneel et al. 2003). The government coalitions Balkenende I (2008) showed similar lower participation in (2002) and Balkenende II (2003), as well as more nature conservation if farmers valued land recently Rutte I (2010), have chosen to purchase ownership highly. Another important factor was less and less agricultural land; instead further trust in the government: a result of the fact that increasing the role of private landowners and farmers have to rely on the government for farmers through AES in order to accomplish payments over a set period of years to compensate nature objectives (Jongeneel et al., 2012), and as for the loss of agricultural yields. Other reasons, such prevent the loss of biodiversity. as mentioned by Van Egmond and De Koeijer For these plans to work, however, cooperation of (2005) are a lack of expertise regarding the the farmers is required. In 2003, only 4% of the requirements of nature, as well as the fact that 1 (permanent) nature has no place in the business In addition, the plan was to provide information strategy. on the costs of construction for such habitats, and The CARE project (Climate Adaptation for Rural compare those to current compensation payments arEas) investigates the effects of climate change to see if the construction would be economically on agriculture, but also nature and water feasible; however, absence of suitable data management, as well as possible adjustments to prohibited this, although remarks on the overall these circumstances in order to create a resilient implementability of the adaptations will still be region. The study area of this project is located included. Finally, any benefits for farmers, around the Baakse Beek, a stream in the east of resulting from the presence of the animals or the Netherlands. Here, about 11% of the habitats, will be mentioned whenever applicable. agricultural area is involved in nature conservation (Karssing, 2012). In a recent CARE Initially, Scopus was the main source of suitable meeting, farmers from the area gave their reasons articles, using search terms as “multifunctional for participating (or not) in AES, which among agriculture” AND Netherlands, (“Neomys financial and time-related arguments included a fodiens” OR “water shrew”) AND habitat – or the wish for temporary adaptations. This literature similar (“Hyla arborea” OR “tree frog”) AND study will investigate if such transitory nature habitat. As time progressed, ‘habitat’ was replaced would actually provide benefits for biodiversity, by ‘food’, ‘lifespan’, ‘vegetation’ or ‘dispersal’, as represented by the Eurasian water shrew among others. Some additional terms were (Neomys fodiens) and the European tree frog occasionally added to limit large amounts of (Hyla arborea), both creatures that have shown a articles to only a few interesting ones, such as sharp decline in the Netherlands over the past ‘Eurasian’ to select just those about the Eurasian decades (H. arborea: Vos and Stumpel, 1995; N. water shrew, but as N. fodiens is commonly fodiens: Pellet et al. 2006; IUCN, 2012). referred to as just ‘water shrew’, this was not always preferable. When only a few dozen titles 2. Materials and Methods were left, visual inspection of the titles and/or In determining the scope of this research, several reading the summaries or abstracts helped select factors including time constraints, availability of those that were the most promising. data and use within the CARE project played a Along the way, more articles were obtained role. The latter two resulted in an investigation in through references in other articles. Part of a title the water shrew N. fodiens and tree frog H. (within double apostrophes) was inserted in arborea, as both of these were mentioned as Scopus and, if without result, Web of Science. important species in the project, and enough When neither resulted in the article sought, information was deemed to be available. Google Scholar was used as a last resort. If titles To find out whether temporary habitats could were very general or there was confusion on the provide an option for those two animals, the title and subtitle, an author’s name was usually following questions had to be answered: used, after which the specific article was found by year of publication. References also helped to find ~What are the environmental requirements for this animal (e.g. vegetation, food, humidity, size a number of interesting books or chapters of of area)? books, most of which were available from the Forum Library. Although peer-reviewed articles ~How long do these habitats take to develop? had a preference, some books provided important ~Do these habitats become more suitable as time progresses? key features of some animals not mentioned in the more technical articles (e.g. lifespan) or were ~What are the downsides for the temporary nature of the habitats for the animal (i.e. removal very often referred to in acquired literature (e.g. of housing)? Handoek natuurdoeltypen; Bal et al., 2001). 2 3. Results effect for the presence of some trees, although 3.1 Neomys fodiens relatively few shrews were found if the tree cover was dense. Bank height ranged from minimal to 3.1.1 Habitat and food 3m (shrews occurring more frequently with As its name suggests, the Eurasian water shrew N. banks >1.5m) and with inclinations anywhere fodiens has a preference for sites directly next to from 0° to 90°, with a positive effect for slopes of or at least nearby water, where it both lives and is >45°. active (Voesenek and Van Bemmel, 1984; Lardet, Castién and Gosálbez (1999) found N. fodiens in 1988; Bal et al., 2001). Rychlik (1997) caught 94% the Pyrenees at the edges of a wood (rich in of the water shrews at the water’s edge and the bramble patches and long grasses) and riverbanks, remaining 6% within 0.5 meter from water. Lack but not in moorlands or the beech forest itself. of fresh water has been suggested as the reason Heathlands are also mentioned by Greenwood et for the absence of N. fodiens on several islands in al. (2002) as being avoided by water shrews, Finland (Peltonen et al., 1989). Although poor while even built-up areas were inhabited. water quality has been thought to have a negative effect on the presence of N. fodiens (French et al., N. fodiens is a generalist in terms of food as well: 2001), either directly or by affecting prey a large amount of invertebrate groups (including, availability, Scott et al. (2012) more recently but not limited to: Diplopoda, Araneae, found them to be much more tolerant to Opiliones, adult Coleopterea, Diptera larvae, pollution than suggested, even the combined Trichoptera, Plecoptera) are on its diet, which it effects of phosphate,