Wetlands, the Earth’s kidneys

Wetlands are one of the world’s most important ecosystems. They are referred to as the “Earth’s kidneys” and that comparison could not be more accurate. Wetlands truly are as important to the planet as kidneys are to humans, with one exception: humans can survive with only one kidney, but the Earth cannot.

Kidneys are in charge of humans’ fluid balance. If we are dehydrated, our kidneys try to preserve as much water in our bodies as possible, and when we have excess water our bodies, our kidneys work to discharge the extra water. Wetlands work in the same way. They mitigate both floods and droughts by absorbing and recharging water.

A wetland photographed from a drone. © Antti Nykänen

In addition to fluid balance, kidneys are also responsible for removing unnecessary and hazardous substances, such as waste products and medical substances. In resemblance to our kidneys, wetlands purify our natural waters. They filter and remove nutrients and pollutants from our rain and floodwaters. Extra nutrients will sink to the bottom of the wetland and hence are available for wetland vegetation. Kidneys purify 1750 litres of blood every day, but the water purification ability of global wetlands is 30-fold. Wetlands purify 30 cubic litres of water daily.

Unfortunately, the world has lost approximately half of its wetlands, and Europe alone has destroyed and altered two-thirds of its wetlands. We need strong actions to retain the Earth’s functioning.

The value of wetlands is essential in urban environments, where nutrient and pollutant levels are manyfold compared to more natural environments. Urban wetlands should be seen as important and cheap tools to purify our stormwaters, along with maintaining biodiversity within cities.

A Moorhen (Gallinula chloropus) chick at a wetland in Finland. © Mia Vehkaoja

Luckily, the Ramsar Convention has acknowledged the importance of urban wetlands and themed this year’s World Wetland Day as “Wetlands for a Sustainable Urban Future”. Happy World Wetland Day 2018! Let’s appreciate the Earth’s vital organs.


Whooper swans don’t out-graze wigeons

A few decades ago the whoopers swan (Cygnus cygnus) was an endangered and rare species in Finland. It only bred in remote lakes and people rarely saw them. The population increase of whooper swans after protection is one of the success stories in Finnish nature conservation. Nowadays the swans can be heard gaggling all around Finland. The whooper swan is a large bird, and it thus consumes a lot of vegetation. Water horsetail (Equisetum fluviatile) is one of its favourites.

The whooper swan population has increased greatly, and their gaggling can be heard widely in Finland.

Certain other species also prefer water horsetails. For example, wigeon (Mareca penelope) broods forage within the horsetail growths searching for emerging invertebrates. A study published earlier this year showed that the water horsetail is disappearing from Finnish and Swedish lakes. The reasons for this pattern are unknown, but one possible explanation could be increased grazing pressure. Whooper swans effectively utilize horsetails, and swan grazing was therefore suspected to be influencing the disappearance of the horsetail. Wigeon populations have concurrently shown a worrying decrease.

A recently published study conducted of 60 Finnish and Swedish lakes utilized vegetation and waterbird data gathered in the early 1990s and in 2016. The study area widely covers the boreal, reaching from southern Sweden to Finnish Lapland. The whooper swan population increased strongly during the study period. Researchers studied whether whooper swans’ grazing on water horsetail is causing the negative trend in the wigeon population. Pair counts were used to indicate waterbird communities, and thus any changes caused during the brood time were not shown.

Whooper swans are grazers that have to consume a great deal of vegetation to survive.

The study showed that whooper swans strongly preferred lakes with horsetails during the 1990s, but this connections is not seen anymore. While the number of swan-occupied lakes has increased, the number of horsetail lakes has decreased dramatically. However, it appears that swans and disappearing horsetails do not associate, because the horsetail has also been from lakes where swans don’t occur. The horsetail has increased in some swan-occupied lakes.

The number of lakes used by wigeon has decreased, but swans are apparently not causing this. Wigeon loss has not been stronger on lakes occupied by swans. Quite the opposite, as wigeons and swans appear to positively correlate. Even though wigeons prefer horsetail lakes, their disappearance is not associated with the horsetail loss occurring in the study lakes, which suggests that wigeons can also utilize other lake types. On the other hand, the researchers note that this study  did not considered the critical brood time, when the foraging opportunities among the horsetail growths are especially important. Thus it may still be possible that wigeons are affected by horsetail loss, but this effect only appears during the brood time.

Read more:

Pöysä et al. 2017. Recovering Whooper Swans do not cause a decline in Eurasian Wigeon via their grazing impact on habitat. Journal of Ornithology.

Pöysä et al. 2017. Habitat associations and habitat change: seeking explanation for population decline in breeding Eurasian wigeon Anas penelope. Hydrobiologia.

Blog text: Vanishing wigeons and fading horsetails

Traffic flattens billions of frogs every year

Amphibians are run over by cars more often than other vertebrates. Per road kilometer, an average 250 amphibian individuals die every year because of traffic. According to this calculation, over 113.5 million frogs die annually on the Finnish road network (454 000 km). In Brazil, one of the world’s amphibian hot spots, traffic annually kills 9 420 frogs on each road kilometer. This means a total of over 16 billion frogs lost due to traffic.


Roads built near wetlands are the most significant cause of frog mortality on all continents, but particularly in Europe. No relief is in sight for this problem, because traffic amounts are increasing every year throughout the world.


Fast-moving frog species are somewhat fortunate because their traffic mortality is quite low on roads with little traffic (24–40 cars per hour). Up to 94% of fast-moving frogs survive when crossing a road. Slow-moving species, such as the common toad (Bufo bufo), are not that lucky. Only half of common toads survive to the other side of a road. On busier roads (60 cars in an hour) over 90% of common toads are run over by a car.

A dead common toad (Bufo bufo) hit by a car. © Mia Vehkaoja

Amphibians suffer from both direct and indirect negative effects of road networks and traffic. Mortality is a direct cause, whereas isolation is an indirect cause. Amphibians migrate according to seasons: during spring to their breeding grounds and during autumn to their wintering grounds. These migrations make amphibians vulnerable to traffic mortality. Season migrations occur particularly in the temperate zone, such as in Europe, where traffic has become the greatest threat to amphibian survival in certain places.


The traffic mortality of frogs decreases population sizes and reduces migration, which lead to a decreasing gene flow between populations and the disappearance of genetic diversity. Smaller populations are at greater risk of going extinct.


Historically thousands of kilometers of roads have been built through wetlands, which leads to the disappearance, isolation and depletion of wetland habitats. Roads also influence the cycle and function of water systems. Road construction has drained and polluted wetlands all over the world.


Conservation actions should concentrate not only on restricting road construction laws and regulations, but on preventing frogs from accessing roads by installing culverts and fences. According to a French study, the combination of culverts and fences is the most efficient way for saving frogs from traffic mortality. But this is just one study, and unfortunately we still know too little about which methods are best for amphibian conservation.


Four reasons why beaver wetlands are paradise for pin lichens

Beaver activity enhances the occurrence and diversity of pin lichens (Caliciales). Both the number of species and individuals is much higher in beaver-created wetlands than in other types of boreal forest landscapes. There are four reasons behind this:

1. High amounts of deadwood. Pin lichens grow on both living trees and deadwood. Decorticated deadwood in particular is preferred by pin lichens. Beaver-induced flooding kills trees in the riparian zone and produces high amounts of decorticated snags.

Pin lichen on decorticated stump. © Mia Vehkaoja

2. Diversity of deadwood types. Beaver activity produces snags, logs and stumps. Snags are created by the flood, whereas logs and stumps are also produced by beaver gnawing. The diversity of deadwood tree species is also wide, containing both deciduous and coniferous tree species. The diversity of deadwood types maintains a high diversity of pin lichen species.

3. High humidity conditions. High humidity conditions are favorable for many pin lichen species. Old-growth forests are usually the only places in the boreal forest belt that contain high humidity conditions. There the shading of trees creates a beneficial microclimate for pin lichens. Lighting, on the other hand, becomes a limiting factor for pin lichens in old-growth forests. Most snags in beaver wetlands stand in water, where steady and continuously humid conditions are maintained on the deadwood surface.

Snags produced by a beaver flood in Evo (southern Finland). © Mia Vehkaoja

4. Sufficient lighting conditions. Because most of the deadwood in beaver wetlands stands in water, it is concurrently in a very open and sunny environment. Many boreal pin lichens are believed to be cheimophotophytic (cheimoon=winter), meaning that they are able to maintain photosynthesis also during winter at very low temperatures. The algae member of pin lichens requires enough light for photosynthesis. Open beaver wetlands make photosynthesis possible for pin lichens during both summer and winter. Snow also enhances light availability during winter.

More information: Vehkaoja, M., Nummi, P., Rikkinen, J. 2016: Beavers promote calicioid diversity in boreal forest landscapes. Biodiversity and Conservation. 26 (3): 579-591.


It walks and quacks like a mallard, but does it look like one?

This is a mallard (Anas platyrhynchos). It is your basic duck, familiar from park wetlands. A mallard quack is also the classic duck sound.

Wetland ecology group_University of Helsinki_duck_mallard

A wintering mallard flock is quite colourful: males have green heads with yellow beaks and both sexes have blue wing spots.

Age and season affect plumages

But mallards do not always look like those in the picture above. Males do not always have green heads, nor are females always brownish grey. Depending on the season, and the age and genes of an individual, mallards can look a little different. Downy ducklings resemble the ducklings of all other dabbling duck species. However, they rapidly develop species-specific characters, and young drakes for example develop a hint of green on their head even before all the down has disappeared. In the summertime males briefly change into summer (eclipse) plumage that looks like female plumage. Except that a male beak is still yellow.

Wetland ecology group_University of Helsinki_duck_mallard male_sinisorsa

A young male mallard still has down on his back, while some green is already glittering on his head. Both female and male mallards are brown during summer and autumn. The yellow beak reveals that this individual is a male. © Sari Holopainen

Beak reveals sex

In addition to normal changes in plumages caused by seasons or growth, weird looking mallards can also be found. Their plumages might be different due to changes in their genes or hormones.

Wetland ecology group_University of Helsinki_duck_mallard female_sinisorsa

Light female mallard.

Various phenotypes are rather typical among animal species. These variations are common in mallards, and peculiar individuals can be found especially in cities. For example, females might be light due to mutations. Mutations can work in several ways causing changes in pigment production or in its appearance traits. Lightly coloured mallards produce pigments, but their colour appearance has changed. If an individual does not produce melanin pigments at all, it becomes a completely white albino.

Colour variations are thought to be typical in mallards in city environments, where predator pressure is lower and thus exceptional individuals survive better. On the other hand, mallard farming has potentially produced weird-looking individuals that have escaped and spread their genes to natural populations.

Wetland ecology group_University of Helsinki_duck_mallard_intersexual

Wetland ecology group_University of Helsinki_duck_mallard_intersexual_male_female

These peculiar mallard males in wintering flocks are actually females. The pictures show intersexual females together with two normal males and a female. Moulting males changing their eclipse plumage into nuptial plumage can look similar, but their beak colour once again reveals the actual sex. These pictures were also taken in the middle of winter, when males have already changed to their nuptial plumage.

The beak has an important role in identifying mallard sexes because males have yellow beaks and females have orange-spotted beaks around the year. The beak can also reveal intersexual females. They are individuals that express both female and male outfit. This can be caused by disturbances in female hormone production, or then an individual has both female and male features. Hormones regulate the outfit, and if large quantities of testosterone are produced, male plumage may result. Beak colouration is not as sensitive to hormonal changes and even though a female displays male characteristics, it will still have a female beak.

Hybrid ducks

Wetland ecology group_University of Helsinki_duck_mallard_teal_sinisorsa_tavi

This common teal x mallard hybrid male was coupled with a normal mallard female and defended it against clearly larger mallard males.

Mallard flocks may also have hybrid individuals. Duck species are close relatives, and can thus mix rather easily. Various species mixes are known, for example mallards can mix with common teals, Eurasian wigeons, northern pintails and black ducks. However, hybrids are quite rare, because each duck species have specific behaviours and characteristics that prevent hybridization. But sometimes these barriers collapse, and hybrid individuals are born. Hybrid individuals express characteristics from both original species. Their habits and characteristics typically do not interest individuals from the original species and therefore might not breed successfully.

Hybridization can cause several problems, which in the worst-case scenario can lead to the extinction of the original species. The hybridizations of mallard and black ducks in North America is becoming more common after shifts in their distribution. Hybridization is now threating black duck populations. Alien mallards can also cause a serious risk for endemic duck species and to their gene pool. For example, the Hawaiian duck (Anas wyvilliana) is unfortunately going extinct because of non-native mallards. Survival of the species now depends on protection actions that target the extirpation of all mallards and hybrids from the islands

Wetland ecology group_University of Helsinki_duck_mallard_intersexual_male_female_sinisorsa

Four naturally different mallards wintering in southern Finland. The normal type male was coupled with a normal female. An intersexual and a light female are in the upper part of the picture.

It looks like a duck

This white domestic duck is a descendant of a mallard. © Sari Holopainen

This white domestic duck is a descendant of a mallard. © Sari Holopainen

Mallards are commonly farmed, and several different colour variations exist among the domestic breeds. A white duck known by everyone is also a mallard variant. Farmed mallards have sometimes escaped, and now breed with natural mallards. Extraordinary ducks, resembling mallards more or less, are a fairly common sight in Southern and Central European parks. Alien genes in the natural mallard population become more rare in the northern parts of Europe.

Extraordinary ducks in European parks are probably related to mallards: Switzerland, Germany and Sweden. © Sari Holopainen

Extraordinary ducks in European parks are probably related to mallards: Switzerland, Germany and Sweden. © Sari Holopainen

Read more:

Pär Söderquist: Large-Scale Releases of Native Species: the Mallard as a Predictive Model System

Pictures by Harry J. Lehto, intersexual mallards

Pictures by Pekka Sarvela, colour variations

Ducks Unlimited: Waterfowl Hybrids


Drones conquer biological research

For centuries, biologists have been known for their good fieldwork competence and persistence in data collection. But new technology has now arrived to weaken the strong constitution of biologists, though fortunately not our persistence.

Drones a.k.a. Unmanned Aerial Vehicles (= UAV) have been a hot topic for a while now. Previously talk has mainly concentrated on how drones can be used to deliver mail or pizza, or even used for military purposes. But recently researchers have also begun acknowledging the possibilities that drones offer.

Drones or UAVs are remote-controlled or autopiloted to fly a certain route. © Mia Vehkaoja

Drones or UAVs are remote-controlled or autopiloted to fly a certain route. © Mia Vehkaoja

Drones are, as their more professional name implies, unmanned light aircrafts that usually resemble either planes or helicopters. They are either remote-controlled or can be programmed to automatically fly a predetermined route. UAVs can be used to collect aerial photographs and videos, from which orthophotos and terrain and 3D models can be produced. The National Land Survey of Finland uses laser scanning photos that deliver an accuracy of 50 cm, whereas aerial photographs from drones can provide an accuracy of 1–10 cm. With such accuracies we can almost identify and count individual plant specimens.

An aerial photograph of a beaver wetland taken with a drone. © Antti Nykänen

An aerial photograph of a beaver wetland taken with a drone. © Antti Nykänen

Drone orthophotos make it possible for example to calculate the vegetation and open water cover percentages of a water system, and define the vegetation categories of an area. UAV-produced photos open up new horizons for defining vegetation classes. These classes have previously been categorized pretty roughly e.g. tree stand, bushes and brushwood. But now we can identify vegetation to the family or even genus level.

An orthophoto produced from the aerial photos taken with a drone. © Antti Nykänen

An orthophoto produced from the aerial photos taken with a drone. © Antti Nykänen

UAVs can also be utilized in game animal calculations. For example, they are an easier and faster way to calculate the ducks or geese in a certain area. On the other hand, they also make it possible to observe the nests of raptors from the air, which is considerably safer and faster (no tree-climbing involved) for the researcher, and a stress-free method for the bird. Heat cameras can additionally be attached onto the drone, making it possible to calculate the mammals, such as deer, in dense canopy landscapes. USA and Germany have already used drones to calculate mammal populations. UAVs are best suited for at least hare-sized animals.

Drones are here to stay and their use in research will increase and diversify in the future.  Researchers just need to hold on to their seats and let their imaginations fly.


Crawlers and fliers – how to study forest insects

Studying insects is interesting yet challenging. Determining individuals to the species level


The presence of birch bark beetles can be detected by their unique eating patterns. ©Stella Thompson

nearly always requires capturing them first, although some species, such as the birch bark beetle (Scolytus ratzeburgi), can be identified by the unique pattern they leave on tree trunks. However, it is almost always necessary to use various types of traps to capture individuals if identifying the insect species present at a certain site is the main objective of a study. For example, butterflies are trapped during the night using light traps, and the occurrence of certain protected species can be confirmed using feromone traps that use synthetic lures as bait. Traps can be dug into the ground, lifted high up into tree canopies, or attached to the insides of hollow tree trunks.

As my PhD research I am assessing how beavers affect forest beetle populations. I have several research questions:  do beaver-induced flood zones have different beetle species assemblages than other areas, do the increased moisture and sunlight conditions in the flood zone affect species assemblage, and do beaver areas advance or hinder potential forest pest or protected species. My research combines a game species with widespread effects on its surroundings and forest beetles, several species of which have become scarce and require protection. Beaver-induced flooding and the species’ habit of felling tree trunks may locally disturb forest owners, but my study is looking into whether beavers’ actions facilitate or disturb forest pests. Combining game and insect research is cool, and generates new information on which to base decision-making for future protection measures, beaver population management, and even for using beavers as a natural tool for restoring degraded wetlands and forests.

Window traps are widely used for determining the insect assemblages of sites. Window traps cannot be used to capture specific insect groups, because all sorts of invertebrates ranging from flies to pseudoscorpions and wasps to beetles creep or fly into them. Window traps are very simple: the trap is attached to a tree trunk or set to hang between two trees. Insects crawl or fly into the plastic plexiglas frame and then fall through the funnel into a liquid-filled container at the bottom. The container is filled halfway with water, dishwashing fluid, and salt. The dishwashing fluid prevents the insects from regaining flight, consequently drowning them. The salt helps preserve the insects until the trap is emptied out, which happens about once a month. I have 120 traps spread out at several sites, so every summer I collect about 600 samples.

Unfortunately other creatures may sometimes end up caught in the window traps. So far I have inadvertently captured a few common lizards and a bat. This is always disappointing, because an individual dying for nothing does not advance research or science in any way. In the same way it is frustrating if you unintentionally set up a trap on a tree trunk that an ant colony uses as its route. Hundreds or even thousands of ants may drown in the window trap. As my own study focuses on beetles, I cannot utilize the ants in any way. At least this does not happen very often.

After the trap container has been emptied the gathered sample is sifted through using tweezers and a microscope, to separate the insect groups that I am interest in. Next the individuals are determined to the necessary level. Sometimes determining the family level is enough, but if making conservation decisions or gaining new information on certain species is the goal, it is usually necessary to determine individual insects to the species level. How this is done depends on the order in question, e.g. beetles are often recognized by their ankles and genitals.

Occasionally you come across data deficient species, i.e. species that are not well known or understood. Species, genera, and families are determined using identification keys, which are sometimes incomplete. For example, currently the best key for identifying Finnish rove beetles is in German, and for several families the most complete keys are in Russian. So I’m currently kind of happy that I studied German in middle and high school. I guess next I should begin uncovering the secrets of Russian vocabulary.