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.

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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.

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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.

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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

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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.

Let’s ban lead shot!

The use of lead shot and sinks is a global phenomenon. Only the past decades has

wetland-ecology-group_university-of-helsinki_blog_hazel grouse

Grouse species also suffer from the harmful effects of lead shot. ©Stella Thompson

increased our understanding of the negative effects that toxic lead shot inflicts on ecosystems. As an example, birds die of lead poisoning after eating lead shot. They mistake the ammunition for sand or grit, which they use to aid their digestion. The birds’ gizzards and stomach acids dissolve the shot, causing lead to accumulate in their bones. As little as two lead shots is enough to directly cause the death of a mallard-sized animal.

During the 1980s, the US Fish and Wildlife Service (USFWS) conducted a study on the effects of lead exposure on water birds such as waterfowl. Diving ducks were found to be most susceptible, but lead shot was also commonly found in dabbling ducks, geese, and swans. Long-term monitoring by the USFWS also uncovered negative effects on bald eagle (Haliaeetus leucocephalus) populations, and since then, several studies have found harmful effects to numerous animal groups around the world, e.g. bears, deer, predatory birds, doves, loons, and frogs. International studies also associate lead shot with increased lead concentrations in people who regularly consume game.

A federal ban on using lead shot for waterfowl hunting was issued in 1991 in the US. Since then, 34 states have decreed tighter state-wide bans, e.g. California completely banned the use of lead shots in the home ranges of the California condor (Gymnogyps californianus), and by July 2019 California will completely ban lead shot in all forms of hunting, the first state to do so.

But what is the European Union’s game plan concerning lead shot? A total ban has been proposed, but the motion is currently only a thought, and we are still miles away from actual progress. Several countries in the EU have issued various types of bans, e.g. the lead shot has been prohibited in wildfowl hunting in Finland since 1996. The US also seems far from a federal ban.

So what’s the big deal, why are we not stepping up and pushing forward?

Not everyone has been satisfied with the disappearance of affordable, high quality, and gun-safe lead shot. The lead shot ban has caused a great deal of debate and criticism over the years. Many are hoping to weaken the ban in waterfowl hunting to only concern certain shallow wetlands or very important rest areas along migration routes. Those opposing the ban have based their arguments on several propositions formed in the 1990s, which have since been scientifically proven incorrect:

 

Claim 1: Lead shot is not dangerous, because it is believed to rapidly sink to the bottom of wetlands, where waterfowl cannot reach it.

After initiating the partial lead shot ban in 1991, the USFWS began long-term monitoring of its affects. Lead shot –induced mortality in mallards dropped by 64% in the six years following the ban. And this is a dabbling duck species, which according to studies should not even suffer the most from lead poisoning. The impacts that the ban has had on diving duck populations, which find their nutrition from the bottom mud layer of wetlands, or on small duck species are probably even more pronounced. Lead poisoning additionally causes e.g. reproductive problems, which can lead to long-term population declines even without directly killing all individuals. For example, a French research group found that female teals carry shot in their gizzards more frequently than males do, wherefore females had worse survival rates than males. A study in the US relates 17–46% of the mortality of loons directly to lead shot, while the same estimates for swans and bald eagles are 31% and 12%, respectively. The lead shot ban is estimated to annually save 1.4 million waterfowl in the States alone. In Canada, the lead concentrations found in the bones of water birds lessened by 50–70% following a ban. An although loons are not hunted as game, their population declines due to lead shot and sinks should be taken in to consideration when considering the fate of toxic lead shot.

wetland-ecology-group_university-of-helsinki_blog_teal_mallard

Both teal and mallards suffer from lead poisoning, which besides causing death also causes behavioural abnormalities. This makes individuals more susceptible to hunting. ©Veli-Matti Väänänen.

Claim 2: Alternative shot types (mainly steel, vismuth, and zinc) are inefficient and expensive.

A 2015 study in the US compared the effectiveness of lead shot and two types of steel shot in the hunting of mourning doves (Zenaida macroura). No differences were found in aim, the number of injured escapees, hunter satisfaction, or realized quarry numbers. Necropsies of shot doves revealed no differences in the numbers of through-body shots or average strike depths. Steel shot was therefore found to be accurate enough for dove hunting. A poll study found nearly 80% of US hunters to prefer steel to lead shot, or at least consider the two equally effective. Initially the steel shot sold in several countries tried to mimic the qualities of lead shot. The resulting low muzzle velocities and large ammunition size led to poor hunting success. Higher quality steel shot is currently widely available, but the damage caused by poor shot quality was immediate, and is the only reason why steel shot still carries a bad reputation. Many people tested steel shot once or twice, and returned to illegally using lead shot despite the bans.

Steel shot was additionally about four times as expensive as lead shot when the ban was issued in the US, but rising demand has caused their prices to drop significantly. The same would probably occur in many European countries, where demand to increase.

 

Claim 3: Hunting with alternative ammunition increases the numbers of wounded animals. This has been suggested to happen because of the ineffectiveness of non-lead shot and hunters being unaccustomed to lighter weight ammunition.

The USFWS annually conducts a poll inventorying e.g. the numbers of total hunted quarry and injured escapees. During the 1950s and ‘60s, the number of injured escapees was about 20%, but initially grew to about 24% after the partial led shot ban. However, a few years later numbers dropped down to initial levels, as hunters became used to the new shot. During the last years the level has dropped to 14%. The study conducted on mourning dove hunting success also did not reveal any differences in the numbers of injured escapees. So if European hunters are still performing worse after lead shot bans in their countries, they should perhaps consider looking in the mirror and wondering what’s wrong with their aim.

 

Claim 4: The lead shot ban has decreased realized duck quarries, e.g. because hunting and hunting success have lessened.

To date, there is no scientific proof to back either of these claims. But on the contrary, waterfowl populations have decreased markedly during this same time period due to disagreeable habitat change. Could this, by any chance, be the actual reason for diminishing quarry sizes? Especially as assessments and research show that hunters have in fact not obeyed the lead shot ban very widely. For example, 90% of Finnish hunters are still estimated to use lead shot in waterfowl hunting. About 70% of the ducks shot in Britain carry lead shot in their bodies. This means that the use of steel shot cannot have decreased duck quarries, because steel shot simply isn’t being used.

However, one actual problem is that steel shot cannot be used in certain older shotguns. This has probably slightly lessened the duck hunting enthusiasm of some elderly hunters.

 

Unfortunately, the European Commission wants to focus on only lessening the amounts of lead found in wetlands. The EU has ratified the UN’s Convention on the Conservation of Migratory Species of Wild Animals, so we should be rid of lead shots within three years. Therefore it is fairly questionable that a total ban is currently not being discussed in more detail. A few EU nations, e.g. Denmark and Holland, have executed a total ban, thus preventing the use of lead shot in any forms of hunting. Nothing appears to be happening in the US either. Despite the encouraging results on the number of lead poisoning incidents dropping dramatically, the effectiveness of partial bans is just too weak. An overview from 2015 by the University of Oxford estimates that 50 000 to 100 000 birds die annually from lead poisoning in Britain alone. According to the Finnish Food Safety Authority and the Finnish Museum of Natural History, every third white-tailed sea eagle (Haliaeetus albicilla) death is directly related to lead poisoning. Partial bans are ineffective and their execution cannot be properly monitored. A total ban would also create pressure to develop shot that would work well with older shotguns. Now is the time to finally completely ban lead shots.

 

Additional information

on lead poisoning occurring in several bird species

http://link.springer.com/article/10.1007/BF00119051

http://www.nwhc.usgs.gov/disease_information/lead_poisoning/

 

on the mourning dove study

http://onlinelibrary.wiley.com/doi/10.1002/wsb.504/full

 

on the effects of lead on teals

http://www.sciencedirect.com/science/article/pii/S0006320707001346

The beaver – our wetland rescuer

The beavers (Castor canadensis and Castor fiber) have recovered from near extinction, and come to the rescue of wetland biodiversity. Two major processes drive boreal wetland loss: the near extinction of beavers, and extensive draining (if we exclude the effects of the ever-expanding human population). Beaver dams have produced over 500 square kilometers of wetlands in Europe during the past 70 years.

 

The wetland creation of beavers begins with the flood. As floodwaters rise into the surrounding forest, soil and vegetation are washed into the water system. The amount of organic carbon increases in the wetland during the first three impoundment years, after which they gradually begin reverting back to initial levels. The increase in organic carbon facilitates the entire wetland food web in stages, beginning with plankton and invertebrates, and ending in frogs, birds and mammals.

The previous shoreline is very evident from an aerial photograph. Also the beaver flooded area shows clearly. © Antti Nykänen

The previous shoreline is very evident from an aerial photograph. Also the beaver flooded area shows clearly. © Antti Nykänen

Beaver-created wetlands truly become frog paradises. The wide shallow water area creates suitable spawning and rearing places. The shallow water warms up rapidly, and accelerates hatching and tadpole development. Beaver-created wetlands also ensure ample nutrition. The organic carbon increase raises the amounts of tadpole nutrition (plankton and protozoans) in the wetland, along with the nutriment of adult frogs (invertebrates). Furthermore, the abundant vegetation creates hiding places against predators for both tadpoles and adult frogs.

Beaver-created wetlands are perfect rearing places for frogs. The warm water accelerates hatching and the abundant aquatic vegetation gives cover against predators. © Mia Vehkaoja

Beaver-created wetlands are perfect rearing places for frogs. The warm water accelerates hatching and the abundant aquatic vegetation gives cover against predators. © Mia Vehkaoja

The flood and beaver foraging kill trees in the riparian zone. Deadwood is currently considered a vanishing resource. Finnish forests have an average 10 cubic meters of deadwood per hectare, whereas beavers produce over seven times more of the substrate into a landscape. Beaver-produced deadwood is additionally very versatile. Wind, fire and other natural disturbances mainly create two types of deadwood: coarse snags and downed logs. Beavers, on the other hand, produce both snags and downed logs of varying width, along with moderately rare deciduous deadwood. The more diverse the deadwood assortment is, the richer the deadwood-dependent species composition that develops in the landscape.

Beaver-created wetlands produce  especially standing deadwood. © Mia Vehkaoja

Beaver-created wetlands produce especially standing deadwood. © Mia Vehkaoja

Deadwood-dependent species are one of the most endangered species groups in the world. The group includes e.g. lichens, beetles and fungi. Currently there are 400 000 to a million deadwood-dependent species in the world. Over 7000 of these inhabit Finland. Pin lichens are lichens that often prefer snags as their living environment. Beaver actions produce large amounts of snags, which lead to diverse pin lichen communities. Snags standing in water provide suitable living conditions for pin lichens; a constant supply of water is available from the moist wood, and the supply of light is additionally limitless in the open and sunny beaver wetlands.

 

The return of beavers has helped the survival of many wetland and deadwood-associated species in Finland, Europe and North America. Only 1000 beavers inhabited Europe at the beginning of the 20th century. Now over a million beavers live in Europe. I argue that this increase has been a crucial factor benefitting the survival and recovery of wetland biodiversity. Finland and the other EU member states still have plenty of work to do to achieve the goals of the EU Water Framework Directive. Both the chemical conditions and the biodiversity of wetlands / inland waters affect the biological condition and quality of wetlands.

 

The whole research published here