Problems in paradise: the destruction of Hawaiian species

A few months ago I wrote a post on invasive species in Finland, and in particular on the North American beaver (Castor canadensis). I received a comment on how it is bold (or maybe the commenter meant reckless) to say that almost all invasive species are threatening the native species of the region. I began thinking of this comment, and tried to find some studies that proved that invasive species are beneficial for the subject ecosystem. Unfortunately, I only came up with sad tales. One very devastating example of invasive species is the Hawaiian Islands.

The Hawaiian Islands in the center of the Pacific Ocean are one of the most isolated islands in the world. Their endemic terrestrial species originate from some hundred species that migrated thousands of kilometers over the Pacific Ocean during several millions of years. Because of the immigration bottleneck and isolated evolution, the Hawaiian Islands have become a place for numerous distinctive and fascinating species. But it has also made the fauna and flora of the islands very vulnerable to various disturbances, such as human invasion and human-mediated invasions.

Nowadays almost a quarter of Hawaiian terrestrial species are non-native. Birds have probably suffered the most. Previously there were 11 native goose species in the Hawaiian Islands, but nowadays only one species is left: the nene (Branta sandvicensis), also known as the Hawaiian goose. The same has also happened to the native duck species; just two duck species are left (the Hawaiian duck, Anas wyvilliana and the Laysan duck, Anas laysanensis).

The nene, also known as the Hawaiian goose (Branta sandvicensis), is the only endemic goose species left in the Hawaiian Islands. © Sari Holopainen

The nene, also known as the Hawaiian goose (Branta sandvicensis), is the only endemic goose species left in the Hawaiian Islands. © Sari Holopainen

The main reasons for these extinctions are introduced predators (e.g. the feral cat and mongoose), and feral and game species (e.g. the mouflon, Axis deer and feral pig). There are almost 60 studies on domestic ungulates, but none have demonstrated any positive effects of them on native species. Ungulates stimulate the growth of grass among other things, leading to more grasses and less forest. And all this changes the light regime and fire resistance of an ecosystem. Grazing is therefore destructive to Hawaiian forests and to every native organism living in them. It has also been proven that the invasive vertebrate species of Hawaii have facilitated at least 33 invasive plant species. In addition to damages caused by grazing, feral pigs alter nutrient cycling and accelerate soil erosion.

The main problems caused by feral pigs are alteration to nutrient cycling and acceleration of soil erosion. © Sari Holopainen

The main problems caused by feral pigs are alteration to nutrient cycling and acceleration of soil erosion. © Sari Holopainen

There is still some light at the end of the tunnel, although it might be rather dim. The public has come to aid in the eradication of many species. Scientists and wildlife managers have concurrently begun multi-scale population monitoring, which includes aerial and ground-based visual surveys as well as trail cameras. To intensify and simplify the eradications even further, several hundred kilometers of management fences have been constructed. As an outcome of this some success stories have emerged; the eradication of rabbits and feral goats. Furthermore, the midway islands of Hawaii are now rat and non-native mammal free!

Unfortunately, it has been too late for some Hawaiian ecosystems. A key threshold has been crossed in some regions, and recovery of certain ecosystems may not be possible any longer. The populations of illegally introduced axis deer (Axis axis) have been reduced to some dozens, but their eventual eradication has been problematic, because assessing the number of remaining deers on private properties has proved difficult. The axis deer was introduced to provide game, so private properties owned by hunters act as reservoirs for the deer, from where they can be disperse to clean areas.

The main feral goat eradication was performed in 1980s, and nowadays the Hawaiian Islands are goat free. © Sari Holopainen

The main feral goat eradication was performed in 1980s, and nowadays the Hawaiian Islands are goat free. © Sari Holopainen

To conclude, I still dare say that almost all invasive species threaten native species. Even though some invasive species don’t harm all native species, we are always looking at nature as a complex ecosystem consisting of several species and functions. When introducing an alien species, we will always alter the pristine ecosystem.

Advertisements

Eradicating species – an occasional necessity

If Finland is to obey the EU strategy on Invasive Alien Species (IAS), 10 000 North American beavers (Castor Canadensis) are to come under the trigger. Why is this eradication necessary?

Although invasive alien species, e.g. the American mink (Neovison vison), the ruddy duck (Oxyura jamaicensis) and the Himalayan balsam (Impatiens glandulifera), may seem adorable and interesting novelties, they nearly always threaten the survival of native species. Invasive alien species are harmful to agriculture and forestry, and at their worst can even threaten human health. Sometimes we face the inevitable: the eradication of an animal or plant species.

The most efficient way to minimize the risks is to prevent it spreading to an area in the first place. Australia is probably the most famous example of preventing the spread of alien species, as they even clean the shoes of tourists at the airport before allowing them into the country. Unfortunately no nation has been successful in averting the spread of IAS.

Not that a tough fight isn’t being fought the new EU strategy on invasive alien species took effect earlier this year.

The main aim of the strategy is to aggregate a list of the most pernicious invasive alien species and to repulse them in different ways. Finland has 160 harmful IAS. Whether each of them will be on the EU’s black list remains unclear.

The North American beaver is first in line

The North American beaver is one of the most potential mammal alternatives for the list. The species was brought to Finland in the 1930s to save Finland’s beaver population. Back then the genetic differences between European and North American beavers were unknown, although we now know that the species differ even more than humans and chimpanzees.

The niches of both species are identical. They eat the same nutrition and their damming activities are the same. Both species have identical effects on ecosystems.

There are approximately 12 000 beavers in Finland. Most of them (10 000) are North American beavers, while European beavers comprise only a fifth of the North American beaver population. The North American beaver threatens the existence of the European beaver in Finland. It might eventually competitively exclude the European beaver. Adhering to the precautionary principle and seriously considering eradicating the North American beaver from Finland and Eurasia is essential. An eradication plan has nevertheless been conspicuously absent. An eradication plan for North American beavers would abide to the guidelines of both the IUCN’s and Finland’s National Strategy on Invasive Alien Species.

How to eradicate a species in practice?

A large scale eradication of the North American beaver is possible, at least in theory. Several possible methods could be used simultaneously, such as hunting, live capture, sterilization, reintroduction of the European beaver and population monitoring.

Beaver hunting is also financially tempting. Beaver furs have once again become popular in China, so their markets have a demand for beaver furs. After the sterilization or dead trapping of North American beavers, they should be replaced with European beavers.

But this is not a straightforward process. Although the two species differ genetically, they have a similar effect on the ecosystem. Beavers act as ecosystem engineers and benefit several other species in Finland and elsewhere. The present population size of the North American beaver ameliorates e.g. the green sandpiper (Tringa ochropus), the moor frog (Rana arvalis) and the Daubenton’s bat (Myotis daubentonii). However, if all North American beaver individuals were removed and replaced by European beavers, the eradication would be harmless to Finnish nature. Unfortunately, there is nothing to guarantee the success of the reintroductions.

Finland must begin eradication if the North American beaver is placed on the EU strategy plan on Invasive Alien Species. The activity of citizens and hunters will determine the eradication outcome. The Ministry of Agriculture and Forestry in concert with the Finnish Advisory Board for Invasive Alien Species are in charge of the decisions and eradication procedures.

Genetic pollution – for the benefit or harm of species?

All living organisms carry genes, or hereditary information that they pass onto the next generation. Gene flows occur when this hereditary information is transferred from one population to another. This in itself is a normal spreading of genetic material between populations of the same species, and upholds genetic diversity. The more genetically diverse a population, the healthier and resistant to disease or pests they are.

However, there are situations when this gene flow occurs between species or in non-natural situations. This has been dubbed genetic mixing, or more negatively genetic contamination or pollution. Genetic mixing is not automatically a bad thing. For example, closely related subspecies can sometimes interbreed, producing hybrids. Hybridization diversifies genetic material and hybrids may grow faster or larger, or be less susceptible to disease. Problems arise when species with no previous contact with each other suddenly meet, or when genetically engineered (GE) organisms are able to spread their genetic material unchecked into wild populations. Both are examples of genetic pollution, which can cause serious harm to individual species or entire ecosystems.

Hybridization can be harmful for species with low population numbers. This is particularly the case with invasive native and non-native species, and ferile and domesticated subspecies that slowly smother and degrade the native species. Examples include the highly common mallard (Anas platyrhynchos) interbreeding with several other duck species in Europe and North America and the very endangered spotted owl (Strix occidentalis) native to western United States and Mexico hybridizing with the more common barred owl (Strix varia) that is spreading from the east. In both cases the rare species are becoming even rarer, and many believe that this form of genetic pollution should be prevented. However, these are just cases of normal evolution, and it is difficult to draw a line on what is true conservation and what meddling. If an invasive species begins aggressively dominating native species and hybridizing with them, our first thought is how to stop its spread.

Unidentified duck expressing traits of several species. © Sari Holopainen

Unidentified duck expressing traits of several species. © Sari Holopainen

A more concerning form of genetic pollution occurs when GE organisms exhibit gene flow to native wild populations, e.g. when the pollen of certain GE crops end up dispersing into nearby wild populations of the same crop. This spreading can quickly become completely uncontrolled due to wind or insect pollination, and its effects remain unknown in native populations. The damage caused by GE organisms spreading can involve ecosystems in unprecedented ways, e.g. GE corn has been proved to significantly increase the mortality of monarch butterfly (Danaus plexippus) larvae. This in turns disrupts local bird populations because of lessened food resources.

The key difference between hybrids and GE organisms lies in their ability to occur in nature. The hybridization of two subspecies with one and other is perfectly natural, and happens all the time. Organisms spread into new areas, coming into contact with closely related species. Often times this is purely natural spreading. GE organisms on the other hand are completely man-made, and have no precedence in nature.

GE organisms may have less viable offspring, but this is not enough to curb their spreading in the wild if released uncontrolled. A US study modeled a freshwater lake into which a small number of GE fish were released, and concluded that the GE fish would lead the healthy wild fish population to extinction within 40 years, despite the original wild population being thirty times larger than the GE population. This is naturally only one example of a modeled situation, but the reasons behind the overthrow of wild fish (larger size of GE fish leading to increased mating possibilities) occur commonly among other GE and hybrid populations and can therefore occur frequently in similar situations as well.

Our action plans for dealing with arising problems should be case-specific. Often times the populations suffering from hybridization are already experiencing some other form of stress, e.g. freshwater pollution or the disappearance of old-growth forests. These in turn make these species susceptible to incoming invasives or spreading native species. The original populations may just be too stressed to cope with an additional problem, and so conservations schemes may be called for with certain species and uncalled for with others.

GE organisms however are a different story. We have no clear data on how genetic engineering affects species, how long GE populations can remain in the environment, how easily they transfer the added genetic material to wild populations etc. These are large unknowns when considering their effect on ecosystems and sustainable agriculture, both of which we humans are dependent on.

Domestic goose and greylag goose © Sari Holopainen

Domestic goose and greylag goose © Sari Holopainen

Natural enemies – assistants or catastrophes

Guest author: Samuli Karppinen

The aim of biological control is to use natural enemies for suppressing pest populations. Pest populations include both native and alien species. The natural enemies can be parasitoids, predators, pathogens, antagonists or competitor populations. These natural enemies are called biocontrol agents or briefly agents.

The main aim of biological control is not easy to determine in every case. In agriculture, the aim is to use agents that are beneficial and effective in reducing the pest and which function within the environmental, legal and economic constraints. The use of biological control doesn’t necessarily mean the eradication of the pest populations. Rather, it is a balance between the pests and their natural enemies that prevents the pest populations from expanding to harmful or economically injurious levels. Biocontrol agents can be divided into four classes: classical control, augmentative control, conservation and neoclassical biological control.

The idea of classical biological control is to establish a living organism within an area where it has not occurred before. The living organism can be a natural enemy or competitor of the pest species. The aim of the organism in its new area is to provide pest long-term control. In many cases the target pests are not native species.

The aim of augmentative control or inundative control is to reduce pest population by using sufficient numbers of biological control organisms. In augmentative control, the introduction of organisms will normally need to be repeated.

In conservation biological control, control agents already exist in the target area. The idea of the conservation is to attempt to conserve or enrich the agents. The function of neoclassical biological control is to use exotic non-indigenous agents. The target pests are indigenous. Since they were not in the same area before, this is referred to as a new association.

The ribbed pine borer (Rhagium inquisitor) is a forest pest. © Mia Vehkaoja

The ribbed pine borer (Rhagium inquisitor) is a forest pest. © Mia Vehkaoja

Sterilizing insects is a method of biological control. In this technique huge numbers of sterile, generally male insects, are released into the target area. The idea is that sterile males compete with the wild males for female insects. As a result there will be no offspring and pest populations begin reducing.

Selected natural enemies were previously preferred to be generalists, because non-target species provided alternative food when the target pest was absent. However, the likelihood of attacking non-target hosts is bigger with generalist or polyphagous agents. Nowadays the biological control agent species that are released should be highly specialist predators or relatively host-specific parasitoids. Agent species should control target populations effectively, but they should not affect non-target species. The characterization of suitable biological control agents is difficult because e.g. predator-prey –interactions are very complicated.

Community participation – a key to eradicating invasive alien species

Invasive alien species are a serious threat to both national and global biodiversity. New species might seem fascinating and interesting, but quite often they threaten the existence of native species. Invasive alien species also have impacts on livelihood and economies by damaging agriculture and forestry, as well as infrastructure and human health. They impede native species by one or several ways: eating them, competing with them for resources, interbreeding with them, disrupting or destroying their habitats and introducing new pathogens.

The key to avoid invasions is to shut off every possible entrance pathway. Australia is a known master at blocking the pathways of invaders. However, in reality no country has managed to escape from invasives. The battle against alien species is usually an extensive and long process, which requires a multitude of participants.

One efficient, but surely challenging way to eradicate alien species is community participation. Usually local people are easy to involve in eradication programs when the alien species threatens their livelihood. This was the case of the lionfish (Pterois) in the Caribbean. It has invaded the Caribbean Sea, putting local fish stocks at risk and filling in the catches of fishermen. At first the fishermen didn’t have any possibility of selling this new product, as the locals falsely believed the lionfish to be poisonous. After authorities released their eradication strategy with corrected information and the slogan “Let’s eat it to beat it”, the locals’ involvement in the eradication rose to a great extent. When people gained the correct knowledge, they began eating the lionfish to save the native fish species.

One main challenge in community participation is unawareness. Mostly people don’t even recognize alien species from native ones. So the key is to inform the public. In Finland the Finnish Association for Nature Conservation (FANC) encourages Finns to recognize, prevent and report alien plant species, such as the Himalayan balsam (Impatiens glandulifera) and Persian Hogweed (Heracleum persicum coll.). FANC has even established an internet page http://www.vieraslajit.fi, where the public can report their observations of alien species.

Persian Hogweed (Heracleum persicum) is a harmful alien species to both native species and humans. It causes burnlike damages. © Sari Holopainen

Persian Hogweed (Heracleum persicum) is a harmful alien species to both native species and humans. It causes burnlike damages. © Sari Holopainen

According to FANC the success of alien species eradication lies on the shoulders of every Finn. This statement has been greeted by getting down to business at the University of Helsinki. Each spring students attending the ‘Alien species’ course do their share and remove the very feisty alien species Ramanas Rose (Rosa rugosa) from a beach in eastern Helsinki. The dispersion of Ramanas rose is unpleasant also from the public view, because it is aggressively occupying the beaches of sunbathers.

Successful eradication needs everyone’s effort. Organizing a prevention event is easy. In Finland FANC provides detailed instruction on how, and you can always contact your local environmental authorities for further information and guidelines.

Common water hyacinth is native in Amazon, but it has successfully invated many areas around the world. This picture is from Borneo. Water hyacinth is very problematic alien species, as it covers all open water areas of lakes and ponds affecting dramatically to the function of ecosytems © Sari Holopainen

Common water hyacinth is native in Amazon, but it has successfully invated many areas around the world. This picture is from Borneo. Water hyacinth is very problematic alien species, as it covers all open water areas of lakes and ponds affecting dramatically to the function of ecosytems © Sari Holopainen

Beavers of Finland

We have written some posts about beaver ponds, but in past months I have realized that most people don’t even know that e.g. Finland has beavers at all, and in particular that Finland has two beaver species: the Eurasian beaver (Castor fiber) and the North American beaver (Castor canadensis). Both species came close to extinction in their native habitats during the 19th century due to overexploitation. In Finland the native Eurasian beaver was hunted to extinction in 1868. In 1935 Finland reintroduced 17 individuals of the Eurasian beaver (9 males and 8 females) and in 1937 seven individuals of the North American beaver from New York (3 males and 4 females). Back in those days it was not known that the Castor-genus has two separate species. As recently as 1973 it was discovered that these two beaver species differ in chromosome numbers (C. fiber = 48, C. canadensis = 40). Compared to humans and chimpanzees, which differ in chromosome number by two chromosomes, the difference between the two beaver species is remarkable.

The North American beaver (Castor canadensis) in Finland. © Sari Holopainen

The North American beaver (Castor canadensis) in Finland. © Sari Holopainen

As a result of this duplicate reintroduction, Finland nowadays has approximately 10 000 North American beavers and just 2 000 Eurasian beavers. Why the North American beaver has excluded the Eurasian beaver is not quite clear. The construction activities and body size of both species are similar, but the North American beaver reproduce somewhat more effectively with bigger litter sizes (C. fiber ≈ 2.5, C. canadensis ≈ 4.5). As no other differences have been detected, this higher fertility seems to be the North American beaver’s advantage.

Finland was one of the few countries introducing the North American beaver to its nature. However as a consequence of being introduced to Finland, the North American beaver has also spread out to Russia. As the North American beaver is not a native species in Finland’s or Russia, it is classified an alien species, and is included in Finland’s alien species strategy. The status of the North American beaver as an alien species is quite tricky. Although it has excluded Finland’s native beaver species for the most part, it benefits rather many other native species, such as the common teal (Anas crecca), the moor frog (Rana arvalis) and the Daubenton’s bat (Myotis daubentonii). If we eradicate the North American beaver from Finland, will the Eurasian beaver spread out to the location where the North American beaver has occurred? We can’t know this for sure, but are we willing to take the chance and place the other species benefitting from beaver at risk? One possibility could be that the spread of the Eurasian beaver would be aided by humans. Originally the Eurasian beaver inhabited the entire country, so it has every prerequisite to be distributed to its original range. What strategies Finland’s policy-makers decide to take remains to be seen.

To read more about the eradication plans and shared history of beaver species in Finland and Russia

Parker, H., Nummi, P., Hartman, G. & Rosell, F. 2012. Should (and can) the invasive North American beaver Castor canadensis be eradicated from Eurasia? — Wildlife Biology 18: 354–365.

Or in Finnish
Vehkaoja, M., Nummi, P., Parker, H., Hartman, G. & Rosell, F. 2013. Amerikanmajava Castor canadensis Suomessa ja Euroopassa: pohdintoja vaikutuksista ja mahdollisesta hävittämisestä. – Suomen Riista 59: 52–61.

Outlaw or welcome come back: how to manage returnees

Case wild boar in Fennoscandia

Just a few thousand years ago wild boars were widely spread in Europe, also in Fennoscandia (that is Norway, Sweden, Finland and western parts of Russian Karelia). Then the climate changed, weather got colder and at the same time hunting pressure by humans increased. As a result wild boars disappeared from Fennoscandia, the last ones just a few hundred years ago.

Wild boars are walking back to Finland. This wild boar lives in Finland, in Ranua Wildlife Park where all the animals are found in the Arctic.

Wild boars are walking back to Finland. This wild boar lives in Finland, in Ranua Wildlife Park where all the animals are found in the Arctic.

Lately wild boars have made a comeback to Fennoscandia. The populations in Sweden are originated from captured wild boars and are now also occupying Norway. To Finland wild boars have walked naturally from the southeast, where they managed to maintain populations the whole time. Even though wild boars are on their way back to their historical distributions, their management seems to cause problems.      

Sweden has gone through many phases in the management of wild boars. After a couple of reintroductions and extirpations, in the 1970’s some wild boars escaped from enclosures, and finally established a successful wild population. In the end of 1980’s the Swedish government agreed that wild boars belong in Swedish nature. Now there are around 200 000 – 300 000 wild boars in Sweden. The yearly hunting level has increased strongly, reaching almost the yearly 100 000 quota of the important hunting species, the moose.

Despite the official status of being an indigenous species in Sweden, the neighbours Finland and Norway are still struggling with their view on boars. In fact, wild boars are basically outlaws in both countries!

In Norway wild boars are listed as “a high-risk species” in the Norwegian Black List of alien species. Boars are causing serious concern about their impact to indigenous species. Hunting of wild boars is possible year around in Norway and aims for strong population control. Wild boars are unwelcome returnees in Norway, but at the same time another ungulate that disappeared circa 9000 years ago from Fennoscandia has a different status. Muskoxen have been reintroduced to Norway several times during the past century. Muskoxens are local tourist attractions and even ended up in the coat of arms of the Dovre municipality.

Muskoxen have been reintroduced to Norway, and migrated also to Sweden. Finland has muskoxen in Ranua Wildlife Park.

Muskoxen have been reintroduced to Norway, and migrated also to Sweden. Finland has muskoxen in Ranua Wildlife Park.

In Finland the situation is something between Sweden and Norway. Wild boars are not considered alien species, but their status is still unsure. Boars have been detected in Finland since the 1970’s, but at first all the boars were hunted during the winter. Boars are currently protected during breeding time, but hunting is not regulated and is mostly unsustainable. Some hunting clubs make an exception by sustainably managing local boar populations. Interestingly, not even conservation organizations in Finland have stressed the boar-issue, while for example wolves with the same head number are well presented in conservation agendas.