The stability of ecological corridors as illustrated by examples from Poland

Transcription

1 Gerlée A., 11. The stability of ecological corridors as illustrated by examples from Poland. The Problems of Landscape Ecology. Vol. XXX The stability of ecological corridors as illustrated by examples from Poland Alina Gerlée University of Warsaw, Faculty of Geography and Regional Studies, Department of Geoecology, ul. Krakowskie Przedmieście 30, Warszawa Abstract: The paper presents a method that evaluate ecological corridors stability. It uses the CORINE Land Cover Change data. The method was applied to evaluate stability of ecological corridors linking the Natura 00 network in Poland. Land cover change index and spatial uniformity index were constructed. The analysis was carried out as follows: (1) Assessment of land cover suitability for the migration of large mammals; (2) Evaluation of land cover changes quality (3) Assessment of land cover changes balance within the ecological corridors and beyond them (4) Assessment of changes uniformity in the voivodeships (5) Analysis of positive, negative and neutral changes proportions. The results show that ecological corridors stability differs in analyzed periods ( and 00-06) and regions (voivodeships). Two kinds of stability - static and dynamic were discussed. Strengths and weaknesses of the method were presented. Key words: ecological corridor, landscape stability, land use, CORINE Land Cover Change The aim and scope of the paper The aim of the paper was to assess the stability of ecological corridors in Poland. The term stability does not have one, generally accepted definition. Various interpretations of this term were discussed in an earlier paper (Gerlée 08). For the purpose of this study stability is understood as persistence (constancy) of a given type of land use in time. It is analysed in the context of the function of ecological corridors. Changes in their use are examined in the light of how they might affect the corridors suitability for animal migration. The analysis is based on a proposed network of ecological corridors connecting Natura 00 areas (Jędrzejewski et al. 05, fig. 1) and data from the CORINE Land Cover (CLC) Change database and the CLC Change 00-06, containing information on changes in land cover in the specified periods. Methods The following procedure was applied: (1) Creating a scale of suitability of land cover for migration of large mammals and classification of CLC types; (2) Qualitative evaluation of land cover changes; (3) Evaluation of the balance of land cover changes within and outside of ecological corridors; (4) Evaluation of spatial uniformity of the changes across voivodeships; (5) Calculating area percentage of positive, negative and neutral changes. (1) A five-class division of the types of CLC changes was developed by reducing the 6-level scale proposed by Stachura (03, after Bielecka 07) (tab. 1). I included data on habitat requirements and preferences of large mammals for which ecological corridors have been identified (cf Gerlée 11, Jędrzejewski et al. 04, Jedrzejewski et al. 05, Fleury and Brown 1997, Hilty et al. 06 pp ). (1) A five-class division of the types of CLC changes was developed by reducing the 6-level scale proposed 371

2 Gerlée A. Fig. 1 Regions (voivodeships) in Poland and the ecological corridor network linking Natura 00 areas (after Jędrzejewski et al. 05, modified) by Stachura (03, after Bielecka 07) (Table 1). I included data on habitat requirements and preferences of large mammals for which ecological corridors have been identified (cf Gerlée 11, Jędrzejewski et al. 04, Jedrzejewski et al. 05, Fleury and Brown 1997, Hilty et al. 06 pp ). (2) Qualitative evaluation of land cover changes (k) is based on the difference between land cover ratings on a given area before (Kbefore) and after a change in land use (Kafter), and is calculated with the formula: k = K after K before For example, if in 00 an area was covered by forest (rating 4) and in 06 it was utilised as an open-cast mine (rating 0), the qualitative rating of the change (difference between the two ratings) is -4 (tab. 1). The qualitative evaluation of a change in land cover use can take values from -4 to 4. Table 1. Ratings of suitability of CLC types for functioning as an ecological corridor for large mammals. The table covers all land cover types used in Poland (source: own data) Suitability rating Land cover types (CLC codes in brackets) Continious Urban Fabric (111), Discontinious Urban Fabric (112), Industrial or commercial Units (121), Road & Rail Networks (122), Port Area (123), Airports (1), Mineral extraction Sites 0 (unsuitable areas) (131), Dump Sites (132), Construction sites (133), Green urban areas (141), Sports & leisure facilities (142), Fruit Tree & Berry Plantations (222), Complex cultivation patterns (2) Non-irrigated Arable Land (211), Permanently Irrigated Land (212), Pastures (231), Beaches, 1 (poor suitability) dunes & sand plains (331), Bare rocks (332), Sparsely vegetated areas (333), Burnt areas (334) Natural grasslands (321), Moors & heathland (322), Water courses (511), Water bodies (512), 2 (moderate suitability) Seas & oceans (523) Areas used mainly for farming, with high abundance of natural vegetation (3), Forests and 3 (suitable areas) shrub vegetation under changes (3) 4 (highly suitable areas - optimal suitability) Broad-leaved forest (311), Coniferous forest (312), Mixed forest (313), Inland marches (411), Peat bogs (412) (3) Evaluation of the balance of changes is based on the total land cover changes area with a given rating k( P k ), where k takes the values: -4,-3,-2,-1,1,2,3,4, and the sum of all areas on which changes took place (P). I formulated an index of changes (W z ), expressed by the following formula: 372

3 The stability of ecological... 4 W z = W k k = 4 = Pk W k, where k P Evaluation of the balance of changes excludes changes in land cover that have the same suitability rating (are in the same rating class). In this case the final rating (the sum of all changes ratings) is 0. The index value of 4 means that on a given area 100% changes have rating 4, while the index value of 4 means that all changes on the area have rating 4. The 0 value indicates that positive (with positive sign) and negative (with negative sign) changes cancel out. I also examined the difference in the index value (Rwz) between the earlier (W z ) and the later period (W z00-06 ), where: R wz = W z00-06 W z This index shows a trend of changes and allows to assess whether the situation is improving (positive difference) or getting worse (negative difference) in time. (4) The index of changes uniformity (W r ) is the difference between the area percentage of changes in the corridors of a given voivodeship (Z k ) and the area percentage of corridors in this voivodeship (W k ), and it can take positive or negative values. It is expressed by the formula: W r = Z k W k The index of uniformity allows to examine whether a network of ecological corridors has undergone greater changes than the area outside of the network. The 0% value means that the sum of percent areas on which changes took place in corridors is exactly the same as the percent area of corridors. Positive values mean that changes in the area of corridors prevail. Negative values mean that there are more changes outside of the corridors. Furthermore, I analysed the difference in the changes uniformity index (Rwr) between the earlier (W r ) and the later period (W r00-06 ), where: R wr = W r00-06 W r This difference shows whether in the later period the prevalence of changes within the corridors network increased (positive value) or decreased (negative values) compared to the earlier period. (5) I calculated the percentage of areas with negative (values between -4 to -1), positive (1 to 4) and neutral (0) values in each voivodeship, separately for the areas in and outside of ecological corridors. Results In the area of ecological corridors the highest balance of changes index (Wz) was observed in the Pomorskie and Zachodniopomorskie voivodeships between In this period the lowest index values were obtained for the Opolskie and Śląskie voivodeships. In areas outside of the ecological corridors network the highest values were recorded in the Podlaskie voivodeship between and in the Małopolskie voivodeship between The lowest values were recorded in the Łódzkie voivodeship in both periods and in the Opolskie voivodeship between (tab. 2). Differences between change indices (Rwz) for each voivodeship (within the ecological corridor network and outside of them) are shown in figure 2. The uniformity index (Wp) in corridors was calculated for two cases: 1) for all changes (including those considered neutral) and 2) for considerable changes (i.e. for positive and negative changes, excluding neutral changes), in both periods under study. The obtained results clearly indicate predominance of changes within ecological 373

4 Gerlée A. corridors (positive values). Only in one case (Pomorskie voivodeship) was the index negative, which indicates a tendency to changes outside of the corridors network (tab. 3). outside network within network Wz RWz Wz RWz Zachodniopomorskie Wielkopolskie Warmińsko-mazurskie Świętokrzyskie Śląskie Pomorskie Podlaskie Podkarpackie Opolskie Mazowieckie Małopolskie Łódzkie Lubuskie Lubelskie Kujawsko-pomorskie Dolnośląskie Index Area of analysis Table 2. The balance of changes indices (Wz) and differences between the balance of changes index (RWz) for each voivodeship. The highest and the lowest values in a given region within and outside of the ecological corridors network are in bold (source: own analysis) , ,09-0, , ,57-0, Fig. 2. Difference in the balance of changes index between and within and outside of the network of corridors, by voivodeships Figure 3 presents differences between changes uniformity indices in the two periods: and 0006, for each voivodeship. This analysis shows that if all changes are taken into account, in half of the voivodeships a positive and in the other half a negative trend of changes within ecological corridors is observed. If only considerable changes are included, the prevalence of changes is lower. It can be noted that between there is a higher percentage of neutral changes than between 0006, both within and outside of the ecological corridors network. In both periods within ecological corridors a higher percentage of considerable changes (positive and negative) is observed, compared to the area outside of corridors, where a relatively higher percentage of neutral changes is observed (fig. 4). 374

5 The stability of ecological... Małopolskie Mazowieckie Opolskie Podkarpackie Podlaskie Pomorskie Śląskie Świętokrzyskie Warmińsko-mazurskie Wielkopolskie POLAND Łódzkie Zachodniopomorskie Lubuskie Considerable changes All changes Considerable changes All changes Lubelskie Change type Dolnośląskie Periods Kujawsko-pomorskie Table 3. The trend index (expressed as percent) for all changes and for considerable changes in the analysed periods. Minimum and maximum values are in bold (source: own analysis) Fig. 3. Changes in the trend index in the later period (00-06) compared to the earlier period Fig. 4. Area percentage of negative, neutral and positive changes in each voivodeship and for the whole Poland (by author) 375

6 Gerlée A. Conclusions The stability of ecological corridors, understood as constancy of suitability of an area to function as a migration corridor does not have to mean lack of changes. Two types of stability can be identified here in the first one changes do not affect the suitability of an area (they are given the rating of 0) and in the second one the size and quality of positive and negative changes on a given area cancel out (the balance of the changes index is 0). The results obtained in this study fall between these two extreme cases. Examination of the difference between balance of changes indices allows to calculate a trend between the two periods. However, they should be analysed together with the balance of changes indices, as even though the trend might be positive on some areas, the indices may be different in terms of changes evaluation. This can be illustrated by a network of ecological corridors of the Lubuskie and Wielkopolskie voivodeships. The stability of the ecological corridors network analysed here is more dynamic than of the areas outside the network. This stems more from the fact that negative changes are balanced by positive changes than from neutral changes, which is indicated by the higher (except for two cases) values of the trend index for considerable changes than for all changes. The method presented in this paper does not allow to evaluate the real suitability of corridors for migration as it does not cover barriers such as the transport network, which are crucially important. Furthermore, because of the low accuracy of the input data one can only talk about large scale changes, which point to the nature of changes on smaller areas, not covered by the applied database (CLC). The numeric values of stability (such as those used in this study) should be regarded as relative. In terms of the role in migration the stability of ecological corridors is not optimal for them. Directional positive changes would be more desired. The reasons for the variation in the analysed stability indices should be the subject of further detailed analyses that would include social and economic factors. References Bielecka E. (07) Potential applications of the Corine Land Cover database in landscape mapping and analysis (in Polish) [in:] Importance of landscape research for sustainable development. Geography and Regional Studies Department, Warsaw University, Warsaw CORINE Land Cover (CLC). Web portal [online]. Environmental Protection Inspectorate. Site available in the Internet: (accessed ) Fleury A.M., Brown R.D. (1997) A framework for the design of wildlife conservation corridors with specific application to southwestern Ontario. Landscape and Urban Planning 37: Gerlée A. (08) Stability of natural systems theory and practice, Miscellanea Geographica 13, Warszawa, s Hilty J.A., W.Z. Lidicker Jr., A.M Merenlender (06) Corridor Ecology. The Science and Practice of Linking Landscapes for Biodiversity Conservation. (Part II Key connectivity consideration str.87-5) Washington, Covelo, London. Jędrzejewski W., Nowak S., Kurek R., Mysłajek R. W., Stachura K. (04) Animals and roads. Methods for reduction of the negative effects of roads on wild animal populations. Mammal Research Institute PAS, Białowieża Jędrzejewski W., S. Nowak, K. Stachura, M. Skierczyński, R.W. Mysłajek, K. Niedziałkowski, B. Jędrzejewska, J.M. Wójcik, H. Zalewska, M. Pilot (05) A project of ecological corridors linking the European network Natura 00 in Poland. Publication written for the Ministry of the Environment in the Phare PL project. Mammal Research Institute, Białowieża 376