Constructed wetlands, have been used to decrease nitrogen transport from agricultural catchments to the coast of Sweden, while simultaneously contributing to increased species richness in the landscape. The purpose of this paper is to compile and evaluate data that have been produced in Sweden during some 20 years of using constructed wetlands as an environmental tool. To evaluate effects of different stated objectives for constructed wetlands within different national support systems we focus on nitrogen removal and bird and amphibian species richness. Continuous automatic water sampling for nitrogen removal measurements, during 1.5 to 10 years, has been performed in 7 constructed wetlands located in agricultural catchments in southern Sweden. Nitrogen removal per wetland area varied between wetlands but the results imply that an annual removal of at least 1000. kg. N per ha wetland area can be achieved in individual wetlands. Data from the long-term monitoring of the 7 wetlands, together with nitrogen removal data in the literature, were used to model >150 randomly selected constructed wetlands. According to the modeling, the nitrogen removal per created wetland area varied markedly between different wetland creation programs and was generally considerably lower compared to what can be achieved in individual wetlands. Cost-efficiency of nitrogen removal in wetland creation programs can be increased considerably with improved planning and if other desired benefits (e.g. species richness) contribute to share the costs for wetland creation. The effects of constructed wetlands in Sweden on species number and populations of wetland birds and amphibians were large enough to positively affect the occurrence of species in the national red list, i.e. on a national population level. Species richness of wetland breeding birds in the constructed wetlands were relatively stable after 13 years, but different functional groups had very different succession pattern. The mean maximum breeding bird species number in the wetlands occurred after 3.8 years. Wetland birds and amphibians colonized constructed wetlands irrespective of the original objective of the wetland (nitrogen removal or biodiversity). However, some amphibian species showed preference for biodiversity wetlands. There were clear effects of wetland construction on the regional populations of non-wetland bird species. The maximum species number for a given wetland size was found to be higher than previously reported. The analyses show that wetland construction can be a cost effective method for decreasing transport of diffuse pollution from arable land, and that the wetlands are important for the species numbers and population sizes on all spatial scales. © 2013 Elsevier B.V.

The results of this evaluation show that constructed wetlands in the agricultural landscape are capable of a substantial reduction of the nutrient transport to downstream recipients, but only if properly located. These wetlands will also contribute to an increased biodiversity even if not planned primarily for this purpose. The use of wetlands for multiple functions needs to be developed to motivate large-scale wetland construction.

The Wetland Centre at Halmstad University was commissioned by the Swedish Environmental Protection Agency and the Swedish Board of Agriculture to evaluate the effects of artificially created wetlands in Sweden between the years 1996 and 2002 with regard to nutrient retention and biodiversity. The creation of these wetlands has been financed either by Rural Development Support (RDS: Miva, Project support or Lmiva without Project support) or by Local Investment Programmes (LIP). The results are presented separately for the four different categories of constructed wetlands:

• Constructed wetlands financed by LIP (Local Investment Programmes) (1998-2002).
• Constructed wetlands financed by PS (Project Support) (2000-2002).
• Constructed wetlands financed by Miva (Restoration and Establishment of Wetlands and Ponds on Arable land and Semi-natural Grazing land) (1996-1999).
• Constructed wetlands financed by Lmiva (RDS wetlands that only get management support) (2000-2002).

The main purpose of this study has been to evaluate the extent to which wetlands created by means of these different support systems have contributed to reduced eutrophication and increased biodiversity. The purpose has not been to evaluate individual wetlands but to give an overview of the differences in efficiency between the various support systems and, to some extent, the difference in results between various geographical regions within Sweden. It has therefore been necessary to include a large number of wetlands in the evaluation, which means that extensive field sampling in the individual wetlands has not been possible. The estimates concerning nutrient retention has therefore been based on modelling, and the biodiversity has been assessed by using dragonflies (Odonata) as indicator organisms.

Information on 908 wetlands with a total area of 2860 hectares financed by RDS has been compiled and registered. In terms of area, these wetlands divide into 1815 ha financed by Miva, 920 ha financed by PS and 125 ha by Lmiva. In addition, 274 wetlands created by means of LIP, with a total area of 439 ha, have been registered. Field surveys and sampling has been conducted in more than 100 wetlands randomly selected from this register. It is mainly the results from these selected wetlands that are presented here.

Can it be assumed that a specific environmental constraint imposed on different species leads to a convergence in, for example, morphology? A phenotype expressed in response to external stimuli (e.g. size-reduction in response to mechanical stress) should be adaptive regardless of species – this is largely intuitive, but has been poorly studied. In this issue (pp. 651–660), Puijalon & Bornette reveal exciting new data that suggest that phenotypic plastic responses to identical environmental constraints may indeed be species-specific (Puijalon & Bornette, 2004).

På uppdrag av Naturvårdsverket och Jordbruksverket har Våtmarkscentrum, Högskolan i Halmstad, utvärderat svenska våtmarker anlagda med landsbygdsutvecklingsstöd, LBU-stöd (Miva, projektstöd och Lmiva utan projektstöd) respektive våtmarker anlagda inom lokala investeringsprogram (LIP) avseende näringsretention och biologisk mångfald. Resultaten från utvärderingen redovisas separat för de fyra olika grupperna/kategorierna av anlagda våtmarker enligt nedan (fetstil anger kategorihänvisning i text, tabeller och figurer):

• Våtmarker anlagda med anläggningsstöd inom Lokala investeringsprogram 1998 - 2002, LIP.

• Våtmarker anlagda med anläggningsstöd inom LBU-projektstöd (dessa våtmarker får vanligen även skötselstöd, Lmiva), 2000 - 2002.

• Våtmarker anlagda 1996-1999, utan anläggningsstöd men med skötselstöd (Miljöstöd), Miva.

• Våtmarker anlagda från år 2000 - , utan anläggningsstöd men med skötselstöd (LBU-våtmarker som endast får skötselersättning), Lmiva.

Syftet har främst varit att utvärdera och jämföra hur våtmarksanläggning inom olika stödformer har bidragit till minskad övergödning och ökad biologisk mångfald. Syftet har alltså inte varit att utvärdera enskilda våtmarker utan att ge en helhetsbild för olika stödformer och regioner. Därför har det varit nödvändigt att basera utvärderingen på data för ett stort antal våtmarker. Detta innebär att utförliga mätningar ej kunnat genomföras inom de enskilda objekten. Närsaltsretention har därför beräknats baserat på modeller och biologisk mångfald har undersökts genom att trollsländor använts som indikatorgrupp.

Inom uppdraget har, med jordbruksstöd, registrerats information om totalt 908 våtmarksobjekt om totalt 2860 ha ersatt yta fördelat på 1815 ha Miva, 920 ha projektstöd och 125 ha Lmiva utan projektstöd. Totalt registrerade våtmarker med stöd från LIP är 274 st, omfattande 439 ha.

Kompletterande fältstudier har utförts i drygt 100 st våtmarker. Främst är det resultaten från dessa våtmarker som sammanfattas nedan...

The central role of macrophytes for the functioning of aquatic systems means that the most effective way to manage these systems is often through vegetation management. For this we need to understand the mechanisms regulating vegetation distribution. Submerged macrophyte distribution is mainly related to water depth, water transparency and epiphytic growth. The distribution of emergent vegetation can largely be predicted from water depth and substrate characteristics. Also, in both submerged and emergent macrophytes, the effects on the vegetation of grazing can be dramatic. Management should aim at providing environmental conditions favouring the desired ecosystem state, rather than methods directly aimed at the vegetation. For example, the best method for promoting establishment of emergent vegetation is often lowering of the water level. To establish submerged vegetation, water transparency can be increased through biomanipulation (the removal of zooplanktivorous fish leading to increased zooplankton grazing pressure on phytoplankton). Changes in water depth and introduction of grazers are often effective measures to control growth of aquatic weeds.