No, more wetlands will not lead to malaria epidemics in Sweden!

The risk of getting back malaria in Sweden is sometimes suggested as a real concern in discussions regarding large state-funded efforts to re-create wetlands to mitigate climate change or reduce eutrophication and increase landscape biodiversity. The latest we have found regarding this is from a magazine published by Derome where a professor in history, Kalle Bäck, calls the risk of malaria a “terrible consequence that nature conservationists have missed”, see attached article (in Swedish). The problem is that he is completely wrong.

Anders Lindström at SVA, the National Veterinary Institute states:

“It is a strange statement about malaria that Kalle Bäck makes. Firstly, it can be stated that the malaria that existed in Sweden in the 18th and 19th centuries was caused by Plasmodium vivax. The parasite that Bäck refers to as causing the most deaths in the world is Plasmodium falciparum, that is, a completely different species. P. falciparum has never been found in northern Europe because it is too cold here for the parasite to develop in the mosquitoes. Plasmodium vivax can certainly also kill infected humans, but to a much lesser degree. During the period 1749 – 1820 an average of 1045 people died per year from malaria in Sweden. The disease was endemic and common along the coast from Blekinge up to Ångermanland and around Mälaren and Vänern. When there were epidemic outbreaks, it appeared all over southern Sweden.

The species of malaria mosquitoes responsible for the spread of malaria parasites overwinter as fully grown female mosquitoes. You can still visit almost any stable attic and find malaria mosquitoes. The dredging of wetlands certainly reduced the population of malaria mosquitoes, but as I said, the mosquitoes are still there and are not rare.

The fact that malaria disappeared in Sweden is considered mainly to be due to better housing standards. The mosquitoes thrive in dark and damp stables. When the housing standard was lower, there was no major difference between animal houses and residential houses. Often the animals were outdoors all year round. When the houses became warmer, brighter, cleaner and with lower humidity than before, the mosquitoes preferred to stay in the increasingly common animal stables. Since malaria mosquitoes almost always bite at night and there is food for them in the stables, fewer people were bitten and the transmission of malaria parasites decreased until it stopped.

The improved health care and the use of quinine also reduced malaria parasites. In order for us to bring back malaria in Sweden, it would be required that we get a significant part of the population infected by malaria parasites and at the same time bring back the 18th century housing standard and that the healthcare system fails to identify and treat malaria cases. “

New arthropod sampling this week

This week Peter and assistant biology student Ellen Nein are doing a new sampling campaign in the 8 wetlands that were emptied this summer and the 8 controll wetlands. This follow-up sampling will also be repeated next year to study more long-term effects of droughts on the arthropod communities in the floodzones of wetlands.

Vegetations survey gave interesting botanical results

The vegetation surveys of ca 25 wetlands are now finished. In total ca 15 submersed species were found, including at least 4 Charophyte species. Among the more interesting findings were the Bryozoa Plumatella repens and 2 Nitella species that are on the Redlist (NT); N. gracilis and N. mucronata. Unfortunately we also found the invasive species Elodea nutallii in some wetlands. Below are some photos of some species. It is clear that constructed wetlands in the agricultural landscape can be important also for threathened and rare plant species, and the the occurrence of invasive species is frequent.

Plumatella repens
Elodea nutallii

Vegetation surveys started

We have started with the surveys of submersed vegetation in the wetlands. This is also part of our networking with the Cyano bacteria project at Lund University run by Pablo Pablo Urrutia Cordero. The macrophytes are surveyed every 10 meters at 2 transects perpendicular to each other in each wetland. It is always interesting to see how the planning (first photo) holds up when it meets the reality of the field work (second photo)…So far so good, Our idea with two persons on the SUP where one handles the GPS to find the right sampling site and does steering and paddling, and one person doing the actual sampling seems to work.

Second sampling in the field experiment

This week David is in Halland to do the follow up-sampling in the field experiment where we have emptied 8 wetlands. He had help from an Intern from the biology course at Stockholm University, Beata Wolgers. Some maintanence of one of the Malais trap was also neccessary since the cattle can be a bit too curious.

Field experiment started (water level manipulations)

This week we started a field experiment where we simulate drought by emptying (lowering the water table) some wetlands. We emptied 8 wetlands and have another 8 as controls. The purpose is to see the effect of drought on the arthropod communities at the shorelines of the wetlands. Peter did the ”pre-drought” sampling with Malaise traps, color bowls, suction sampling and pitfall traps. We also took photos of the wetlands with a drone before and after emptying. After a month of dry-out we will repeat the invertebrate sampling, and also repeat it next year to study long-term effects.

Scientific paper published

The first paper from our surveys is now published. The title is: Insects and spiders in constructed wetlands: interesting findings from a systematic survey in Uppland and southern Halland, and is published in Entomologisk Tidskrift 143 (1–2): 47–66. It can be viewed and downloaded by clicking on the image below:

SEPA`s annual meeting on Wetland ecosystem services held at Halland

The annual meeting for the Swedish Environmental Protection Agency´s research grants on Wetland ecosystem services was held att Hushållningssällskapet Halland/LIFE-Goodstream the 17-18 of March. It was a hybrid meeting with ca 25 persons on site and ca 45 joining digitally. It was a very nice meeting (despite the weather during the field day) and we visited Halmstad University´s experimental set-up aswell as some of our sites in the Buffer project. All the 8 projects presented their work and we got oppertunities to good discussions and networking during the meeting.

Popular scientific article submitted

Today we submitted a short article to inspire the public to explore wetland shorelines in order to experience the high biodiversity of insects and spiders. It is based on the findings in our projects which also are explained in the article. Results on beetles, spiders, flies, dragonflies and pollinators are presented. It will be published in ”Hallands Natur” (in Swedish).

”Half-time” Thesis presentation by David Åhlén

The 19 of November David Åhlén presented results from the Buffer project and the Management project as part of his ”half-time” seminar in his thesis-work at Stockholm University. Opponent was Professor Riccardo Bommarco, SLU. It was a combined live and zoom event and we got to hear interesting discussions on invertebrate food web dynamics at wetland shorelines/flood zones, and effect of management regimes on species abundance and distribution.

A paper on interesting findings from the biodiversity surveys of 2020-2021 has been submitted

Today we submitted the first scientific paper in the project. It is a compilation with commentaries on interesting findings from the biodiversity sampling. It was submitted to the Swedish Entomological Society´s Journal; ”Entomologisk tidskrift”. The title is: ”Insekter och spindlar i anlagda våtmarker: Intressanta fynd från en systematisk undersökning i Uppland och södra Halland” (Insects and spiders in constructed wetlands: Interesting findings from a systematic survey in Uppland and southern Halland).

Conference and work shop in Stockholm

The whole Biowetland project group attended a conference at Stockholm University (Multi-functional wetlands) the 27 of October and thereafter a 2-day workshop with ca 20 researchers discussing a joint paper on Constructed wetlands and synergies and trade-offs of wetland functions. A very good and rewarding 3-day event at Stockholm University and Tovetorp research station. Below are some photos from the conference and the workshop.

Second sampling of invertebrates for 2021

Today David arrived in Halmstad for sampling with Malaise traps and pitfall traps in the 14 wetlands that we will empty next year. This sampling toghether with another sampling next year before emptying will serve as comparisons with samplings done after the lowering of the water levels.

David loads the car with Malaise-traps and other field equipment at our office.

Sorting and identifying organisms continue…

The sorting work is progressing within the project with additional groups fully identified . The very large spider material is now identifed by Raul Vicente, and the dance flies (Empididae) by Sven Hellqvist. Examples from the two organism groups are shown below. Planning for this year’s studies is also in full swing. As we have received funding for nutrient analyzes in Uppland from Bolincentret’s RA3 and RA7, as well as the Albert and Maria Bergström Foundation, we will be able to collect very interesting data to investigate the impact of nutrients on spider and insect communities. We have also received funding for a drought experiment in Halland from Bolincentret’s RA8, and it will be very interesting to see how drought affects spiders’ condition and food preferences.

All the Crane flies (Tipuloidea) are now identified and counted

Another group of insects from the Malaise traps survey in 2020 has now been identified. it is the Crane flies, where we found a total of 47 species in Halland and 39 species in Uppland. Of these, 7 were new species for Halland and 4 new species for Uppland. The most exciting species was Paradelphomyia nigrina, which is a northern species and has only been found a few times in Finland and once each in Sweden (Dalarna) and Norway. The species was found in our traps in Uppland, and identified by Michael Andersson, Sweden’s leading expert on Crane flies. He has also taken the photo below

New species for Sweden in our sampling!

The first results from last years sampling of invertebrates have now been delivered by the experts that have spent the winter sorting, counting and identifying the specimens. One group that has been done so far is the family of dancing flies (Empididae). Among the specimens was a species never encountered in Sweden before! It is the fly Hilara manicata. Apart from this new species for Sweden, also 3 new species for the County (Halland) were found. Several organsim groups remain to be counted and identified, e.g. spiders and beetles and it will be interesting to see if we get more surprises.

Sorting of samples

Now the sorting of the samples is on the way. Victor Eriksson is hired to sort out the groups of interest, that will later be sent out to experts for species determination.


The collection of arthropods is done for 2020! The season has been very rewarding, with more than 550 samples collected between the 75 total wetlands in Halland and Uppland.


When doing sampling close to livestock, you always have to anticipate setbacks. The cattle at this location close to Båstad on the border between Halland and Skåne, showed a particular interest in trampling the Malaise trap, twice!

Last collection this year

The last collection of the year in Halland is now on the way with Malaise trapping and suction sampling. Just east of Halmstad, close to Årnarp we found this Wasp spider (Argiope bruennichi) which is a rather recent immigrant to Sweden.

Collection spiders

In Uppland we are also collecting spiders for gut content analyses. The process is similar to that of the suction sampling, only we are using an InsectaZooka and exchangeable collection socks to minimize the cross-contamination risks, as well as cleaning the equipment with bleach. This concludes the sampling period in Uppland for 2020 in late-August.

Third collection

The third and last leg of collection is on the way, with Malaise-, and pitfall trapping, as well as with suction sampling in both Uppland and Halland. Seen here is the pitfall trap that measures 7cm in diameter and 6.5cm deep, and is filled with soapy water; mounted at Senneby wetland, close to the Baltic coast north of Stockholm.

Second collection

The second collection, with more Malaise-trapping in both Uppland and Halland is now in action. After the hot-streak during the midsummer week, we hope to find plenty of insects around the wetlands. This picture is taken at Hemmesta sjöäng, a reconstructed wetland east of Stockholm.

Inverted leaf blower

Collecting ground living arthropods using an inverted leaf blower is an effective way to gauge the density of their communities. The spiders and insects that get sucked up is transferred to a white tub, from which it is easy to pooter-out the individuals of focus.

Arthropod collection

The start of the years arthropod collection! The collection methods we use are suction sampling, pitfall trapping, and Malaise trapping. The tent-like trap is a Malaise trap, invented in the 1930’s by René Malaise, and optimized for catching flying insects. The collections will be done at 25 wetland locations in Uppland, and 50 in Halland (see distribution in Project Area section). This trap is placed at a constructed wetland at the Bergianska garden, just west of Stockholm University.

BioWetland is launched

Welcome to BioWetland!

Wetlandscapes & Biodiversity – Buffer, Biodiversity and Bees

Research on how constructed wetlands(CWs) function hydrologically in a river basin perspective and how hydrology and its interactions with wetland design, location and management affect the biodiversity in wetlands and at the landscape level, with focus on arthropods in terrestrial-aquatic boundaries and pollinators.