As a result of various activities of human some damages has occurred in nature. The excessive use of natural resources increased depended on the industrial revolution and as a result irreversible environmental pollution formed. The opinion of accepting the environmental problems as Ainternational" instead of Anational" gets important and it is understood that urgent measures must be taken to prevent or decrease the degradation in nature.
The starting point of solving the environmental problems and the nature conservation is to know and describe the problems. Almost every country carries on various studies on describing the environmental problems (Anonymous, 1998).
It is important to analyses and evaluates the relations between land sources and land uses to provide conservation and sustainable development of natural resources. The most common method is Aecological risk analyses". Ecological risk assessment is process for systematically evaluating how likely it is that adverse ecological effects may occur as a result of exposure to one or more stressors. The goal of ecological risk assessment is to help understand the relationship between stressors and ecological effects to inform risk management decisions (Anonymous, 2003).
Ecological risk analysis was firstly applied by Bachfisher et al. (1977) in Germany. According to Aulig et al. (1977) the quantity of interactions among the present uses and planned uses should be determined in grades. Thus the negatively being affected risk of important ecologically biotopes and the other elements by various activities is exposed.
The ecological risk analysis is applied in a few fields in Turkey. The studies of Köseoglu (1981), Altan (1982), Altan (1991) and Yücel (1997) on this subject are available.
In this study, ecological risk analysis is applied to Gala Lake which is one of the important wetlands in Turkey by considering the mentioned studies.
In this study the determination of ecologically sensitive areas is aimed by determining the uses which destroy the biotope potential of Gala Lake and the ecological effects originated from these uses. For this purpose, the suitability, the sensitivity and the negative effect as regards biotope potentiality are determined and according to the result the ecological risk mapping is prepared.
MATERIALS AND METHODS
Gala Lake is chosen as material in this study (Fig. 1). The Meriç River, which constitutes the border between Turkey and Greece, forms a large delta and several small lakes are located. Gala Lake located in Thrace Region of Turkey and 10 km to the north of Enez. Gala the major lake on the delta, consist of two sections, Büyük (or Big) Gala and Küçük (or Small) Gala. Lakes Pamuklu and Meriç and the two Gala Lakes are all interconnected. Pamuklu Lake to the northeast of Gala Lake is covered with reeds. Gala Lake has a big water mirror in the research area. Reeds are mostly seen in the edge of the lake, but Küçük (or Small) Gala Lake is mostly covered with reeds (Fig. 2). Gala Lake is in the borders of Meriç Delta, which was announced as class A type wetland according to international criteria and announced as ANature Conservation and Site Area". The north part of the area is used as rice paddies, the foothill of the Hisarl2 Mountain is covered with bushes and forests.
The basis of ecological risk analysis is consist of the interactions among the different complex land uses and the analysis of the interactions between the natural potentiality and land uses. This interaction is formed by the relation among the uses which destroys the land, the effects formed by these uses and the components which are destroyed by these effects (Altan, 1991; Yücel, 2001).
Ecological risk analysis method is formed by four different phases which follows each other. Determination of ecological risk, sensibility against the negative effect and intensity of negative effect forms the two important phases. According to Bachfischer, the sensibility against the negative effect is depended on the usage of the sources in the area, the quantity of the suitability of these uses and the reaction of the land to these effects. This concept qualitatively describes the suitability of the natural potential of the land for the various land use. Quantitatively, the amount of the suitable land uses to the land gets important (Altan, 1991).
The other concept is intensity of negative effects. The intensity of the effect is depended on the land use which is the source of negative effect and the state of the negative effects formed by this land use. The intensity of the negative effect is determined by two factors. The first one is the sort and the quantity of the negative effect and the second one is the condition and the distribution of the natural factors in the area (Altan, 1991).
Another concept for determining the ecological risk is Athe suitability" for land use. The suitability and sensitivity are related with each other. If the natural potential is suitable to the land use then the sensitivity is low, if not then sensitivity is high (Yücel, 2001).
When the intensity and sensitivity which are effective in obtaining the risk are evaluated together the risk of the negative effect can be indicated in grades. The risk gets lower when the sensitivity and intensity get lower. It is impossible to make a numerical evaluation since the criteria which play role in determining the ecological risk is ecological factors, instead of this it is possible to make comments by using grades (Yücel, 2001).
In the first step of this study the grades for sensitivity and suitability are made by using evaluating factors for biotope potential. Various evaluating factors are considered in determining the suitability and sensitivity.
In the second step a graduation is made to determine the sensitivity which is necessary to display the degrees and the amount of the effects. The grades are determined as Ahigh sensitive" Amedium sensitive" Alow sensitive".
Afterwards, potential negative effect is displayed by determining the negative effects and their intensity and sensitivity against these negative effects. To display the degree of effects a graduation of Ahigh intensity" Amedium intensity" and Alow intensity" is made. The potential negative effects and suitability for uses are evaluated together and the ecological risks were displayed.
In the last stage of the study data are transferred from 1/25.000 scaled maps to 1/50.000 scaled maps. By considering the suitability and sensitivity for biotope potential, suitability is given by cross-hatching and the sensitivity of the biotope potential is given by coloring. The criteria of suitability and sensibility are given in the same map but the risky areas against ecologically negative effects are given in a transparent map which is put on the main map. The risky areas are determined depended on the degree of correspondence of suitability and sensibility.
Ecological risk analysis for biotope potential of Gala lake: Biotope is defined as a homogeneous living medium where is evident separated from the other environments (Çepel, 1995). Biotope potential is the wealthy of the species and varieties of flora and fauna in an area.
The state of being effected from the pressures in the environment and suitability and sensitivity of the biotopes of Gala Lake which provides living mediums for important bird species is determined individually.
Suitability: The biotope potential of the research area is consist of existing flora and fauna in the area. Kantarci (1988), Anonymous (2000a) and Anonymous (2001) were referred to determine the flora of the area. Besides data which was collected in the area studies were evaluated. The area has three structurally different ecosystems which are; water ecosystems, half-terrestrial ecosystems and terrestrial ecosystems. In Table 1 the flora of Gala Lake and Pamuklu Lake is given.
The criteria from Red Data Book prepared by IUCN in 1994 were used to determine the species in danger and the endemic species (Anonymous, 2000b). There is not any endemic species in the research area. According to the criteria of IUCN Trapa natas L. (Trapaceae) in the Pamuklu Lake environment is in the group of Avulnerable" species. This property makes the area more important.
The area is not only important because of the plant communities but also because of the potential of providing living mediums, accommodation and protection zones for birds. Various studies are available about the research of bird species of Thrace region. In the studies on Gala Lake different numbers of bird species are given. According to Anonymous (1991) the number of bird species is 112, it is given as 111 in Anonymous (2000a), 146 in Ertan (1994), 134 in Kaya (2000).
Three bird species of 134 is in the group of A.1.2, 23 in A.2, 30 in A.3, 21 in A.4, 6 in B.2, 10 in B.3. A total number of 93 is in the ARed List". A.1.2 includes the species of Turkey which are critically endangered, A.2 includes the ones endangered, A.3 includes the ones threatened, A.4 includes the ones near threatened, B.2 includes the ones migrating over Turkey or winter visitors of Turkey which are endangered, B.3 includes the ones migrating over Turkey or winter visitors (Kaya, 2000).
Cygnus olor, Grus grus, Alcedo atthis are the winter or summer visitors but not the native species of Gala Lake defined as critically endangered species of Turkey in ARed List".
The native species of Gala Lake which are endangered in Turkey are; Podiceps nigricollis, Phalacrocorax carbo, Pelecanus onocrotalus, Egretta garzetta, Aquila heliaca, the ones winter or summer visitors but not native species are Podiceps ciristatus, Podiceps grisegena, Phalacrocorax aristotelis, Pelecanus onocrotalus, Pelecanus crispus, Botaurus stellaris, Ardea cinera, Ciconia nigra, Tadorna feruginea, Tadorna tadorna, Charadrius dubius, Hoplopterus spinosus, Chlidonias hybrida, Chlidonias leucopterus, Streptopelia turtur, Coracias garrulus, Upupa epops.
The endangered migrating bird species over Turkey or winter visitors are Podiceps auritus, Mergus merganser, Calidris ferruginea, Gallinago gallinago, Tringa erythropus, Tringa ochropus.
The threatened migrating species over Turkey or winter visitors are; Calidris minuta, Limosa limosa, Numenius arquata, Tringa nebularia, Tringa glareola, Larus minutus, Larus ridibundus, Larus genei, Larus canus.
According to Ongan (1994) the fish fauna of Gala Lake is represented with 16 species which are; Perca fluviatilis L., Rutilus rutilus L., Cyprinus carpio L., Scandinius erythrophtalamus L., Carassius auratus L., Esox lucius L., Abramis brama L., Tinca tinca L., Aspius aspius L., Stizostedion lucioperca L., Bilicoa bjoerkna L., Lepomis gibbosus L., Leuciscus cephalus L., Anguilla anguilla L., Siluris glanis L., Astacus leptodactylus. Esox lucius, Stizostedion lucioperca L. ve Anguilla anguilla L. have economic value. Perca fluviatilis L., Rutilus rutilus L., Cyprinus carpio L., Scandinius erythrophtalamus L., Carassius auratus L., Abramis brama L. are fishing species. Besides the fish species, the lakes in the area also include turtle, frog and water snake species.
Otto-Zimmermann determined the suitability for biotope types flora and fauna as Ahigh" Amedium" and Alow" in the suitability classification of biotope potential as regards biotope types (Table 2) (Yücel, 1997). Biotope mapping which has an important role in determining the biotope potential for biotope mapping has been prepared by us (Fig. 3).
The Küçük Gala Lake and Pamuklu Lake have characteristic biotope structure in the protection zone. The north part of the ANature Conservation and Site Areas" has rice paddies in places. The suitability classification of the area is given in Table 3. According to this table the wetlands and the areas protected by legal arrangements are determined as Avery suitable", the waters and forests rich by the nutrition as ALess suitable", the areas poor by the species as Anot suitable".
Sensibility: The sensibility of the biotope potential is the reaction of the biotopes against the present or possible external interferences and against the hindrances which blocks its functions in landscape.
||A view of Kucuk Gala Lake
||Type of Biotope
||Ecological risk map of Biotope Potential of Gala Lake
|Table 2:||Suitability classification of biotope potential as regards biotope types (Yücel 1997)
|Table 3:||The suitability classification of Gala lake biotope potential
|Table 4:||The sensibility classification of the biotope potential of Gala lake
|Table 5:||The intensity of the negative effects
|Table 6:||Determination of potential negative effects
|● Highest potential negative effect, ! Higher negative effect|
|Table 7:||Determination of ecological risks
|■Highest ecological risk, ■ Higher ecological risk,
■ Medium/low ecological risk
The sensibility criteria of the area are given in Table 4. Sensibility of any biotope has a close relation with the suitability of this biotope. The sensibility of the biotope becomes higher depending on; the sensitivity of the ecological balance of the biotope, the number of the endemic species and the species in danger of disappearance, the hard conditions for biotope to renew itself. From this point of view, Gala Lake and Pamuklu Lake is classified as Ahigh sensible", wetlands and Hisarl2 Mountain as Amedium sensible", agricultural fields as Alow sensible" (Fig. 4). The road planned to be built from Enez to 1psala increases the sensibilities of the biotopes in the ANature Conservation and Site Areas".
Negative effect: In the research area the pressure due to the present uses on the biotope potential is the usage of chemicals (pesticides and fertilizers). The plant and animal species especially birds and fishes are under excessive pressure. Besides the drainage systems causes important function loss in wetlands. Another land uses that affects the biotope potential are the road from Enez to 1psala which is partially structed and the stone and the stone quarry. The ecological risks are determined as follows by considering the suitability and the sensibility of the biotope potential and effects.
First of all the intensity of the negative effects according to the present and planned land uses are determined (Table 5).
In the second step, Apotential negative effects" are determined by considering the intensity of the negative effects and the sensibility of the biotope against all the land uses on the area (Table 6).
Lastly, the ecological risks are determined by considering the potential negative effects and the criteria of suitability to nature of biotope potential (Table 7). This Data is collected and transferred to the map given on Fig. 4.
Ecological risk for biotope potential in the study area is determined for Nature Conservation Area and Sites as Ahighest", for marshes and Hisarl2 Mountain as Ahigher", for rice fields as Amedium/low" (Fig. 5). Since the Nature Conservation Area and Sites has sensible characteristic biotopes it is determined as high risky areas. 93 of 134 bird species of the area are in the ARed List", this expose the importance of the area as regards conservation.