Considerable knowledge has been acquired on the design and improvement of pond landscapes of high value for amphibians, thanks mainly to three LIFE projects.
The first project dealt with the consolidation of the European fire-bellied toad Bombina bombina in Denmark (LIFE99NAT/DK/006454).
The two other projects, still ongoing, focus on the protection of the Great crested newt Triturus cristatus in the Eastern Baltic region LIFE04NAT/EE/000070) and on the management of the Bombina bombina in the entire Baltic region (LIFE04NAT/DE/000028).
With basic experience on turtle conservation in Lithuania, Poland and Germany, there are enough data available to implement protection measures on herpetological (reptiles and amphibians) sites of European interest and to develop a concept of active protection of sites of high herpetological diversity in the North European lowlands.
Main threats to the habitats/species targeted within the sites involved in the project
1. Habitat fragmentation and migration barriers
Habitat fragmentation and isolation populations contribute to an alarming loss of viability in Emys orbicularis, Bombina bombina and Triturus cristatus populations, affecting their demographic as well as genetic nature.
In Germany most of the Emys orbicularis-populations are smaller than 4 individuals and not viable. Especially, in the case of smaller local populations, a regular individual exchange between the local populations is vital for their long-term survival. Each local population of Emys orbicularis needs a cluster of ponds and close to them several nesting sites for short-term survival. The ponds can vary in their suitability for mating, foraging or hibernating. Only a small number of all Lithuanian (< 10 % of all populations) and all Polish (< 10% of all populations) and even no German Emys orbicularis localities have enough number of individuals for short-term survival of populations.
The suitability of ponds for Triturus cristatus and Bombina bombina can also vary e.g. in the egg survival and larval development. “Productive” or “source” ponds produce lots of young newts and toads while “unproductive” or “sink” ponds may not contribute to reinforcement of populations. Sometimes, ponds where surveys have shown lots of newts and toads to be present are less productive, while those that are less obviously occupied by adults in the spring can produce more young. In all project countries, only a small number of Bombina bombina (< 15 % of all populations) and Triturus cristatus populations (< 20 % of all populations) inhabit suitable habitats with small clusters of ponds, forming real metapopulation.
2. Loss of water bodies
Most suitable water bodies for Emys orbicularis and amphibian species were lost during the land reclamation. Now, more than 80 % of the local populations of Emys orbicularis in Lithuania and Poland and 100 % of the German populations are small (< 30 individuals) and dispersed. The actual situation of water bodies doesn’t allow bigger population sizes. In cases of complete loss of turtle habitat animals were forced to spread upon artificial ponds near farms and villages which are very often unsuitable because of size and structure of water bodies, disturbances by man, pollution and locations to roads. If individuals lived there isolated from other population members, mating and successful reproduction respectively is reduced or prevented. The total situation will lead to further isolation and decline of Lithuanian and Polish turtle populations like it already happened in Germany.
Large amounts of small water bodies being suitable for breeding of Triturus cristatus have disappeared in Lithuania, Poland and Germany. As a result Triturus cristatus can often be found only in single isolated water bodies (the distance between breeding ponds is often more than 1 km). This gives rise to doubts concerning the survival of the species, as a single water body situated far away from other similar ones is exposed to great dangers. In Lithuania e.g., only 4 sites out of 35 can provide small clusters of ponds, supporting a meta-population. Breeding ponds in all the other localities are situated separately and in virtual isolation.
3. Overgrowth of water bodies
Due to overgrowth water bodies will be filled in and disappear. This means a total loss for all species depending on water. The overgrowth by bushes and trees in particular at the shore destroys suitable basking sites for turtles. Emys orbicularis needs water bodies with sunshine exposure for obtaining solar energy especially after hibernating, during reproduction period and for growing of juveniles. Males require more energy for higher activities during mating period and females for developing eggs. Turtles in the northern ranges with short summers have also to use solar energy more intensively than turtles in South-Europe. Consequently, the availability of basking sites is a limiting factor for northern turtle populations.
Both Triturus cristatus and Bombina bombina prefers to spawn in water bodies that are at least partially exposed to sunshine. Additionally, those of Triturus cristatus should have clear water and are partially free of water vegetation. Without control and management many types of ponds will overgrow with bushes and dense vegetation, reduce in depth and eventually disappear. Some kinds of water bodies, such as farm ponds or village ponds, have been subject to regular maintenance to prevent succession. When ponds are neglected, they finally disappear. Bombina bombina needs in a similar way as turtles solar energy to mature eggs and build up weight before the winter. Also larvae of Bombina bombina need more warm water than larvae of Triturus cristatus.
4. Loss of nesting areas
Anthropogenic succession causes overgrowing in most of the areas in Lithuania, Poland and Germany. All turtle populations in the three project countries exist in habitats with decreasing numbers of suitable nesting areas. Currently, females in more than 70 % of the populations have to use suboptimal nesting sites e.g. on shaded places, on arable land, far away from ponds etc. Low temperatures in the nests cause prolonged embryo development and incubation or even the dying off of the hatchlings. In the northern species range of Emys orbicularis the reproduction is not successful every year, but additionally lack of incubation success in unsuitable areas and loss of individuals is a big danger for the long-term viability of smaller northern turtle populations.
5. Lack of hibernation sites
In unsuitable conditions during winter time the fitness of the population members and of the total population of Emys orbicularis decreases and becomes vulnerable. Individuals can die. Far dispersed hibernation sites separate turtles and can diminish successful mating next spring. As the winter period lasts long in Lithuania and Poland and as the temperature may fall greatly, the presence of suitable hibernation spots plays a crucial role in the survival of the species. Consequently, the availability of suitable hibernation sites is a critical factor for the viability of Emys orbicularis populations, because this also affects the total number of population members and especially the reproduction success.
Long winter periods in Lithuania and Northeast-Poland with greatly falling temperatures means that breeding ponds of amphibians must be connected with the presence of suitable hibernation spots. In Germany, where the landscape is with larger fields, the distance between hibernation site and pond is often to long for successful survival of the amphibian populations. Thus the hibernation sites in the terrestrial habitat also play a crucial role in the survival of these species.
6. Loss of terrestrial habitat
The loss of terrestrial habitats affects some parts of Emys orbicularis life e.g. nesting, basking and migrating. It can reduce reproduction success and decrease fitness of individuals due to a lack of solar energy. In exceptions, it can also influence and render more difficult movements between ponds which is a space use strategy of Emys orbicularis to fulfill all habitat requirements, and finally it can diminish movements between local populations and individual exchange respectively.
Amphibian habitats become consequently fragmented, which reduces the area for viable populations and finally the population sizes. Together, habitat fragmentation increases the distances between local populations and hinders the flow of individuals between such sites, potentially affecting the genetic and demographic nature of a population. It is very difficult, if not impossible for Bombina bombina and Triturus cristatus to penetrate thick brushwood. As a result, these populations become
isolated and less viable.
7. Intensive agriculture
Due to intensive agriculture the habitats of Emys orbicularis, Bombina bombina and Triturus cristatus become fragmented. Habitat fragmentation causes increased distances between sub- or neighbouring populations. With reduced individual respectively genetic exchange and increased isolation the viability of those populations distinctly decreases. At the same time the loss of suitable habitats minimizes the areas for viable populations and the possible population sizes in an area.
For Bombina bombina and Triturus cristatus it is impossible to penetrate an intensively managed farmland. When amphibians pass a fertilised area the fertilisers stick to their moist skin and the salts dissolve. Fertilising-salts are absorbed through the thin skin of the newt and kill it in the short time. Direct pesticide-spray may kill Emys orbicularis and amphibians but the reduction of food items e.g. invertebrates probably produces an even more severe effect on herpetofauna. The pesticides can contaminate the pond and thus destroy the ecosystem, which the juveniles and adults of Emys orbicularis and the larvae and adults of Bombina bombina and Triturus cristatus depend on.
8. Pretation on nests
In the northern regions reproduction success is impossible every year because of the climatic conditions. So, a high predation rate can be harmful for very small and isolated populations. The loss of suitable nesting sites connected with special requirements to nesting sites can force females of a population to use one place. For predators it is easier to find nests in such concentrated areas, which consequently can be crucial for small and isolated populations.
The current situation in the northern regions shows that in most of the cases the populations are smaller and exist in bigger distances to neighboring populations which makes an individual exchange more difficult. Together, a high predation rate clearly decreases reproduction success and can prevent the growth of small populations respectively cannot prevent a negative population development. This means that such populations cannot improve their own population viability and cannot exclude the high danger of extinction.
9. Fish introduction
Aquatic plants are of great importance as the habitat or shelter of much of the invertebrate fauna and the shelter for young Emys orbicularis, too. Fish can have a significant effect on plant growth. Bottom-feeders uproot plants and create turbidity. Consequently, fish existence influences the invertebrate abundance in a water body. Fish also have a negative impact on the water quality.
Fish stock in ponds has a negative influence on reproduction success of Emys orbicularis, Bombina bombina and Triturus cristatus or even prevents reproduction success of amphibians. Reproduction success of Emys orbicularis can be distinctly impaired by fishes as predators of and competition for young turtles. A side-effect of fish introducing is fishing. Turtles can die in basking traps under water or become life-threatening injured by fishing-hooks.
The eggs and particularly larvae of Triturus cristatus are susceptible to predation by fish because larvae like to gather in open water. No breeding success has been recorded in ponds where Triturus cristatus appears together with fish. Fish also makes big damage to Bombina bombina and Hyla arborea populations by eating their tadpoles.
10. Lack of public environmental awareness
If people do not have appropriate information concerning these species behavior and habitat demands, they can have a negative impact on these species and the viability of their populations. Local people can destroy amphibian ponds e.g. they can populate even very small amphibian breeding ponds with fish, let the ponds grow over, use pesticides and fertilizers or harm them in some other way – without knowing that
Emys orbicularis is threatened by taking away individuals from small and often isolated populations for keeping them at home. After keeping at home turtles can be released in unsuitable habitats e.g. big lakes and/ or far away from their (a) population. Especially, catching of reproductive individuals can impair the reproduction success and the viability of very small populations. During nesting period when local people search for fruits or cut hay and trees close to nesting sites, they can disturb females during egg-laying. Such females can be diminished in their fitness and their reproductive output due to stress.
11. Lack of international co-operation
Emys orbicularis is threatened and declining in all European countries where it occurs. But lack of international co-operation on the conservation and management of Emys orbicularis let as to make a little progress in species conservation. In order to make progress in the species conservation is need to overcome obstacles such as: inadequate and misdirected financing, inappropriate policies and weak supporting institutions, which interfere with progress in managing populations and ecosystems. Lack of capacity, knowledge, and skills in some countries can be a barrier to the adoption of new conservation techniques or suitable management for Emys orbicularis and also for threatened amphibian populations.
Due to the lack of the adequate international attention, inappropriate management and lack of local capacity, relatively stronger populations of subspecies of Emys orbicularis still existing in such countries as Lithuania and Poland could be completely lost. Without appropriate concern of international authorities to the declining of Emys orbicularis and threatened amphibians (e.g. Triturus cristatus, Bombina bombina, Pelobates fuscus and Hyla arborea) in the East Baltic Region and without free flow of specific information among conservation managers, appropriate measures for conserving the following species could delay for 10-20 years, that could be crucial for these species.
