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

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Golden eagles deter foxes, facilitate forest grouse

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Top predators can have surprising effects on ecosystems. Golden eagle @Sari Holopainen

The effects of top and mesopredators on lower levels of food webs have been researched from many perspectives, but less focus has been given to the roles that avian top predators play on mid-sized mammalian predators. The cascade effects of raptors, which concurrently affect several trofic levels, have also gained little attention. However, researchers at the University of Turku have observed how the golden eagle (Aquila chysaetos) affects pine marten (Martes martes) and red fox (Vulpes vulpes) populations, along with the cascade affects induced on black grouse (Tetrao tetrix) and hazel grouse (Tetrastes bonasia) populations.

Golden eagles hunt black grouse, red foxes, and pine martens. When the opportunity arises they will also catch hazel grouse, but because of their smaller size and habitat preferences (thick forests), hazel grouse are better protected from golden eagles, which prefer open territory when hunting. The researchers initially hypothesized that the golden eagle would locally lessen the numbers of red foxes and pine martens, thereby causing a positive affect on the two grouse species.

However, the truth is not quite as simple. Pine marten and red fox densities actually increase in areas with large numbers of golden eagle. One possible reason behind this surprising result could be the large prey populations available for all three predators in these areas, along with the partially overlapping habitat preferences of pine marten and golden eagle. On the other hand, pine martens avoid open territory, possibly because of the non-lethal deterrent effect that golden eagles exert on pine marten.

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Top predators can have surprising effects on ecosystems. Golden eagle @Sari Holopainen

But the story doesn’t end here: high densities of golden eagles still does have an effect, as larger numbers of young hazer grouse and black grouse are present at these sites. The golden eagle may therefore facilitate the grouse by lessening the numbers of mesopredators in their territories through the deterrent effect. This would lead to less predation and egg eating by the pine marten and red fox. In other words, red fox and pine marten avoid golden eagles so effectively, that the two grouse species benefit from their weakened predation performance. A similar protective effect has also been observed with the goshawk (Accipiter gentilis).

Increasing golden eagle territory and offspring densities cause decreasing numbers of black grouse, but this does not occur with hazel grouse. The small size of the hazel grouse most likely protects it from golden eagle predation. The black grouse, on the other hand, favors open territory. Golden eagles therefore appear to have a protective effect on juvenile hazel and black grouse individuals, while threatening adult black grouse.

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Black grouse lekking @Stella Thompson

The cascade effects directed at these grouse species do not appear to change with fluctuating pine marten and red fox densities. The presence of other mesopredators, e.g. raccoon dogs (Nyctereutes procyonoides) and the American mink (Neovison vison), has been suggested as the reason for this. The effects of these other mesopredators were not assessed during the study.

The golden eagle affects mesopredator behavior without affecting their population densities. A similar deterrent effect has previously been observed from white-tailed sea eagles (Haliaeetus albicilla) on the American mink, and golden eagles most probably also deter minks and raccoon dogs. The eagles additionally deter the movements of other potential egg thieves such as corvids.

Pin lichens — the tiny color blots on deadwood

Have you ever entered a forest and seen a person hugging a tree, peering up along the trunk? From this day onwards you can breathe freely again, because you have just encountered a pin lichen biologist at work, and not some bizarre tree-hugging ritual.

Pin lichen biologist peering up along the trunk. © Stella Thompson

Pin lichen biologist peering up along the trunk. © Stella Thompson

Pin lichens, or more formally known as Calicioids, are a diverse and monophyletic lichen group, which usually inhabits deadwood. As their name suggests, they resemble pins. They are tiny, approximately between one millimeter and five centimeters in size. The best way to observe them is to peer up along the trunk of a tree. The spores accumulate into a mazaedium (a cup-shaped part of the fungi), from which they can cling onto the hairs and feathers of animals, or passively disperse otherwise. The spores can be recognized as soot-like dust on your fingers.

Pin lichens growing on deadwood. This species Mycocalicium subtile can be identified with often paler infested area than the surrounding wood. © Mia Vehkaoja

Pin lichens growing on deadwood. This species Mycocalicium subtile can be identified with often paler infested area than the surrounding wood. © Mia Vehkaoja

Although it is relative easy to observe pin lichens with the bare eye, species identification is usually conducted using a loupe or microscope. Further observation opens an entire new world of colors. The algae parts of many pin lichen species are brightly colored in yellow, green, or red. On other species, the stalk of the fungal part forming the actual pin structure can also be quite colorful: white, green, yellow, or brown.

Rust-stained pin lichen (Chaenotheca ferruginea) thrives on conifers, and it is quite widely distributed in temperate to cool temperate areas of the Northern Hemisphere. © Mia Vehkaoja

Rust-stained pin lichen (Chaenotheca ferruginea) thrives on conifers, and it is quite widely distributed in temperate to cool temperate areas of the Northern Hemisphere. © Mia Vehkaoja

There are approximately 70 different pin lichen species in Finland, but unfortunately they are a very deficiently studied group. Some species are parasites. They sponge on e.g other pin lichen species or mosses. Even pin lichen fossils have been found within amber. Using these fossils we are able to model the tree structures of forests that grew over a million years ago. This tiny, yet fascinating, species group deserves to receive more attention. Furthermore, observing them is relatively easy, because they don’t move and make a run for it. All you need is a pair of sharp eyes.

The voice of an ecologist and nature conservationist has fallen silent – Professor Ilkka Hanski 1953-2016

Finnish nature research lost its best known voice after the passing of Ilkka Hanski. Hanski, who made a long and impressive career, contributed to population, evolution and nature conservation biology. The Metapopulation Research Centre, led by Hanski, is focused on studying the effects of fragmentation on species ecology and evolution. The Glanville fritillary butterfly (Melitaea cinxia) is the model species for this research, and lives in meadows and pastures of the Åland Islands in Finland. The butterfly research helps to understand how populations occupy and disappear from fragmented patches (pastures and meadows), and how this affects the features occurring in these populations. In addition to Åland, Hanski has ongoing studies in Madagascar and Borneo. These dung beetle studies have focused on speciation processes and the effects of forest loss on species viability. In his last years Hanski also studied the influence of natural biodiversity on human well-being. For example, biodiversity was found to affect the occurrence of asthma and allergies. Hanski was awarded several prizes for his career, the latest being the BBVA Foundation Frontiers of Knowledge award of Ecology and Conservation Biology earlier this year.

The Glanville fritillary butterfly acts as a model species for the metapopulation theory. The family groups of larvae spin silken webs for their protection. © Sari Holopainen

The Glanville fritillary butterfly acts as a model species for the metapopulation theory. The family groups of larvae spin silken webs for their protection. © Sari Holopainen

Wolf population management – problems in every direction

The wolf is currently quite the hot potato in Finland. In fact, wolves are such a burning topic, that finding neutral information on the current state of the species and on hunting it can be difficult.

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Wolf pup in Polar Park, Norway. © Sari Holopainen

Wolves form packs of several individuals to optimize their ability to hunt moose and deer, their staple food. A pack is run by an alpha pair, or a male and female wolf that have mated for life. The other individuals in a pack do not produce offspring, and young individuals may wander between packs to find mates or raise their position in the hierarchy. Alpha pairs are what keep a pack together.

The wolf is designated an endangered (EN) species in Finland, and strictly protected in the European Union (EU). The Finnish wolf population grew during the early 2000s, due to increased protection and additional individuals moving in from Russia. This increased both the incidence of damage caused by wolves (e.g. to hunting dogs) and the number of wolf sightings around human habitation, leading to dissatisfaction in wolf conservation measures and increased poaching. The wolf population began declining in 2007 due to widespread poaching, which in turn angered conservation organizations and the EU. Since then the wolf population size has seesawed back and forth, and confrontations between various interest groups have escalated.

To alleviate the wolf conflict, the Finnish Ministry of Agriculture and Forestry decided to implement a two-year trial wolf hunt in 2015–2016, aimed to control the population. The effects of the cull will be evaluated after this period. The trial cull is based on a wolf management plan, which attempts to incorporate both the requirements of people living in wolf territory and that of wolf conservation. The management plan is territory-based, meaning all actions are planned per wolf pack and territory.

The management plan determines the smallest viable wolf population as 25 breeding pairs. The Natural Resources Institute Finland (Luke) will produce an estimate for the country’s total wolf population, and based on this evaluation the Ministry determines the largest yearly quota that can be culled using population control permits. However, this quota does not automatically have to be reached.

Population control permits are granted for hunting young individuals, which most likely have the smallest impact on the vitality of a pack. These permits can also be granted for hunting problematic individuals that e.g. repeatedly enter yards or come close to humans. Population control permits can only be granted to target wolf packs that produce litters, or in special conditions on packs in areas where the species has a stronghold. In addition to population control permits, wolves can also be hunted with special permits granted for damage control or by law enforcement. These two permit types are granted only when dealing with problem wolves.

Wolf population fluctuations and management will continue to cause problems in the future. Various interest groups have lost trust in each other and in the Ministry’s wolf management plan. Accommodating both the protection and management of an extremely endangered top predator is very difficult in a situation where said species also causes damage to and fear in certain interest groups. Additionally, protecting the Finnish forest reindeer (Rangifer tarandus fennicus), another extremely endangered species, requires straightforward action plans in terms of the wolf. Population levels of the Finnish forest reindeer are believed to have suffered because of the dense wolf population in the district of Kainuu.

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Wolf in Polar Park, Norway. © Sari Holopainen

The complete protection of the wolf, a management regime in practice at the beginning of the 2000s, obviously failed to work. The population grew initially, but was quickly bulldozed by unsustainable poaching. The population decreased up to 15% a year between 2006 and 2010. The population was approximately 250–270 individuals at the end of 2006, but by the end of 2007 the level had dropped to 200. Complete protection of the species crossed a line in Finnish society, after which poaching was used as an excuse for preventing future damage – a situation that should not be allowed to form. Returning to a similar conservation model would require intensive intervention to stop poaching.

The two-year trial cull was completed at the end of February. Luke evaluated the Finnish wolf population at 220–245 individuals prior to the trial period in 2015. Two hunting seasons later, in March 2016, population levels were estimated at 200–235 individuals. When looking solely at these numbers, the cull has managed to keep the population fairly level. However, 43 wolves were shot during the two-year cull, and over half of these (24) were over two-year-old individuals. It is easy to see that the cull has not met its goal of only targeting young individuals. In fact, a staggering 21% of the culled individuals were alphas. And this level may still increase once age determination is complete for all the culled individuals. Such a high number is unsustainable in terms of future hunting management.

Culling each of these alphas has either caused the weakening or disbanding of a pack, leading to higher numbers of individuals or small groups of wolves roaming around unable to optimize their hunting. This is exactly the way to create more problem wolves that willingly come close to human habitation or begin killing hunting dogs. Additionally, several worrying cases have surfaced, where wolves have intentionally been driven towards habitation or have been deliberately wounded to gain more population control or damage control permits for hunting these “problem individuals”. The goal of the wolf management plan is to uphold a viable population in Finland, but at this current rate, the trial wolf cull also appears to have failed.

What next? The future of the wolf cull will be determined during the fall of 2016. The wolf is obviously a species that causes so many societal conflicts, errors in management, and people taking the law into their own hands, that we need to question whether the wolf should remain a species that can be hunted by the general public. Nevertheless, the wolf population does need both management and protection in the future. Perhaps Finland should consider a model where wolf hunting is carried out solely by the (game) authorities. The population control process could remain the same as before, which would allow the cull of problematic individuals and the regulation of pack sizes. But the professional skills of the proper authorities would ensure that overreactions and the killing of alpha individuals could be prevented, which in the long-term could help stabilize the whole population and mitigate wolf-human conflicts.

4 reasons why vanishing deadwood is a great catastrophe

Deadwood amounts have dramatically declined all over the world. Here I present four reasons why deadwood is so important:

1. Deadwood remains in the forest for a long time
When wood decays, it transforms into carbon dioxide, water and minerals. These are exactly the materials that a living tree binds during photosynthesis. The complete degradation of a tree takes 50 to 100 years in northern regions. Deadwood therefore remains a part of the forest ecosystem for a long time, thus enabling the survival of species depending on deadwood as a substrate.

2. Deadwood is nutrition for fungi and invertebrates

Fungi are the main decomposers of deadwood, but bacteria and invertebrates also take part in the decaying processes. These organisms have special digestive compounds, enzymes, to cut the wooden structure into more easily digestible forms. This works in the same way as the enzymes in our own stomachs that cut the food we eat into more usable shape. Fungi can be divided into three main decomposer groups: white, brown and soft rot. White-rot fungi, e.g. Phellinus nigrolimitatus, lives mainly on deciduous wood, whereas brown-rot fungi, such as Coniophora olivacea, are mostly in charge of decomposing conifers. Beetles (Coleoptera), ants (Formicidae) and termites (Isoptera) are examples of invertebrates that use deadwood as a form of nutrition, but e.g. pin lichens (Calicioid) can also more or less decompose wood.

Pin lichens (Calicioids) grow on deadwood surface. © Mia Vehkaoja

Pin lichens (Calicioids) grow on deadwood surface. © Mia Vehkaoja

3. Deadwood is home for animal offspring
Deadwood is home for thousands of species. For some species deadwood can be an incubation place and a safe nest for newborn offspring. Several beetles and termites lay their eggs inside deadwood, where the hatching larvae are safe in their own chambers. As for Nematocera, Brachycera and Aculeata, the deadwood-decomposing fungi functions as a rearing place for larvae. In addition to invertebrates, birds, bats and flying squirrels (Pteromys volans) also use the holes in deadwood as nesting places. Furthermore woodpeckers (Picidae) as cavity nesters are a good indicator for deadwood abundance.

Several beetle species lay their eggs inside deadwood. © Mia Vehkaoja

Several beetle species lay their eggs inside deadwood. © Mia Vehkaoja

4. The disappearance of deadwood creates local extinctions at the very least
Nowadays deadwood is a dying natural resource. Forestry has decreased the amount of deadwood in Finnish forests by over 90%, concurrently causing the local extinctions of several species. Species that depend on deadwood throughout their entire lives are at greatest risk. Such species include the fungi Phellinus igniarius and the three-toed woodpecker (Picoides tridactylus).

City wetlands, do they create a mosquito problem?

Stormwater treatment wetlands are becoming more and more common elements in urban areas. But does this mean we will soon have thousands of annoying mosquitos as our neighbors? Not necessarily.

Mosquito larvae occupy seasonal forest ponds, where predation pressure is weak. © Sari Holopainen

Mosquito larvae occupy seasonal forest ponds, where predation pressure is weak. © Sari Holopainen

Mosquitos can be a real nuisance around their emerging environment. While more stormwaters are treated by city wetlands, there is serious concern about a growing mosquito problem. They are not only a nuisance, but can also spread diseases.

Several studies have been conducted to control mosquitos in urban wetland areas. Certain methods are apparently capable of limiting mosquito breeding in stormwater facilities, but overall results remain controversial.

What do mosquitos need to occur? Firstly, mosquito larvae need standing water to evolve. Secondly, because larvae are especially desirable prey for fish, mosquitos succeed better in shallow waters without fish. Stormwater management planning should therefore avoid small seasonal standing water patches. Deep ponds without vegetation support fish populations, and are therefore recommended for stormwater wetlands. If shallow ponds are utilized, they should have flowing water and combined to deeper patches.

A dragonfly on its territory in a stromwater wetland. © Sari Holopainen

A dragonfly on its territory in a stromwater wetland. © Sari Holopainen

The effect of vegetation is complex. As already said, fish predate in areas without vegetation. Mosquitos also reproduce well in dense monocultures such as cattail stands. However, another research studying the effect of vegetation in water tanks found that vegetated water tanks had higher invertebrate species diversity. Non-vegetated tanks had low diversity, but maintained high numbers of mosquito larvae.

It seems that successful mosquito control in wetlands relies on species diversity. A diverse food web will produce competition and predation. Thus the creation of breeding habitats for amphibians, fish, and dragonflies controls mosquito production. In laboratory tests water bugs and odonate larvae consumed more mosquito larvae than other tested prey items. Planting herbaceous plant species will tempt dragonflies to the spot. Amphibians breed in shallow waters with vegetation to attach their spawn to. They may be highly successful in areas that are too shallow and vegetated for fish. Amphibians are actually more successful in fishless ponds, with less fish predation and competition. Mosquitos are food for several other species too, and for example measures supporting bird and bat communities around wetlands may help reduce mosquito levels.

Bird families consumes huge numbers of mosquitos during their breeding seasons. A tit couple eats over ten kilograms of mosquitos yearly. This robin nested near an invertebrate rich beaver pond. © Sari Holopainen

Bird families consumes huge numbers of mosquitos during their breeding seasons. A tit couple eats over ten kilograms of mosquitos yearly. This robin nested near an invertebrate rich beaver pond. © Sari Holopainen

Several studies have concluded that well-designed constructed wetlands in urban areas do not create mosquito problems. Wetlands should not be opposed due to mosquitos, but citizens should demand that wetlands are planned to incorporate healthy ecosystems.

Read more:

Mosquito control for stormwater faciilities

Water Resources Management and Water Quality Protection