UFC Universidade Federal do Ceará, Departamento de Geografia and Departamento de Biologia, TU München, Chair of Landscape Ecology

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1 Geo-Ecological Analysis and Assessments of Degradation in the Municipality of Tauá Microregião dos Inhamuns Ceará - (Brazil) Oliveira, V. P. V. de 1, Bezerra, C. L. F. B. 1, Printz, A. 2, Cruz, M. L. B. da 3 1 UFC Universidade Federal do Ceará, Departamento de Geografia and Departamento de Biologia, 2 TU München, Chair of Landscape Ecology 3 UECE - Universidade Estadual do Ceará Abstract The WAVES program (Water Availability and Vulnerability of Ecosystems and Society in Northeastern Brazil) aims to show optimization strategies for life quality in the semi arid Northeast of Brazil. Therefore, the dynamic of ecological and socio-economic processes, including global (climate) change is analyzed and modeled. The study area of the WAVES program comprises the States of Piauí and Ceará with approx. 400,000 km 2. Two reference regions were selected for detailed studies. The working group Landscape Ecology of Ceará concentrated on one of them, the municipality Tauá-Ceará with an area of approx. 4,000 km 2. Tauá is known as one of the driest regions within the semiarid Sertão. As water availability as well as the fertility of soils is very low and erratic, conditions for agriculture are very unfavorable. Besides the natural site conditions, strong impediments to social and technological development and innovation are the persistence of powerful traditional oligarchic structures, illustrated by a very polarized distribution of farm sizes. Subsistence farming on very small farms is the economic reality for the common peasants of the region. Thus, life quality is precarious and most people miss even satisfying stability of survival conditions. Thus, emigration seems since long to be the only answer of the local population, especially in times of droughts. As in many semiarid regions (at least initially) animal husbandry basing mostly on wood grazing is the agronomic key activity in the Sertão. Even if the endemic dry forest, called Caatinga, shows an astonishing ability for regeneration, the limits of overgrazing are rapidly passed in semiarid regions. In Tauá, nowadays degradation is already abundant, although it is more aggravated near settlements. The Landscape Ecology working group Ceará analyzes the complex interrelation of geo-ecological site conditions and land use to detect degradation and desertification processes and to define finally sustainable development strategies. A special focus is on the detection of typical correlations of vegetation and soil types. A four step approach (analysis, aggregation, integration and application phases) combines both deductive ( top down ) and inductive ( bottom up ) methods. To be able to deal on landscape scale, point and transect studies serve as ground check for the interpretation of satellite image data. Data is processed by a Geographical Information System (GIS). Results are represented in maps. Vegetation studies, delineation of landscape units well as estimations on erosion susceptibility are the first results of the study. The data can be linked to spatial units and provide the necessary data input for MOSDEL (an integrated simulation MOdel for Sustainable DEvelopment of Land use), which is foreseen to be transferred to Tauá. Besides the adjusting of the results to the models structure, the next phase, erosion estimations will be checked on base of watersheds. Keywords Landscape Ecology, Vegetation transect, Sustainability, Degradation, Integration, Tauá, Inhamuns, Ceará, Brazil, WAVES 1 The reference region Tauá (State of Ceará Brazil) The reference region, the municipality Tauá is situated in the administrative microregion of the "Sertões dos Inhamuns"-Ceará (see Fig. 1). Fig. 1: Situation of the reference area Tauá-CE The municipality of Tauá is dominated by the ecological unit Semiarid backland depression of the Inhamuns (with a mean of approx. 400 m above sea). In Tauá the headwaters (Trici and Carrapateiras) of the Jaguaribe river, the largest 743

2 and most important river of Ceará, are found. The crystalline basement provides only low infiltration rates and ground water storage capacities (limited to fractures). Thus, the time and quantity of run off is strongly correlated to respective precipitation events: all rivers in Tauá are intermittent. The climatic conditions in Tauá correspond to the typical semi arid Sertão of Brazil s Northeast: a rainy period of only four months and a mean annual temperature of 26 C. Land use is strongly restricted by natural site conditions such as irregular annual precipitation (155-1,474 mm, mean annual precipitation approx. 600 mm) coupled with a high negative annual water balance. Moreover, soils have predominantly a low water-holding capacity and fertility. Thus, acceptable plant cultivations conditions are normally restricted to the small stripes of alluvial soils of the little rivers. If land use management is not carefully adapted to these natural conditions, degradation processes are rapidly initiated which may even lead to irreversible desertification. In Tauá extensive tracts of land are affected by erosion problems. Deteriorating environmental conditions are an important reason for the further impoverishment of the population. Economic activities in Tauá are mostly restricted to small subsistence farming (extractivism and livestock breeding). 60% of the peasants are cultivating on farm sizes of less than 10 ha (3% of total agriculture area), whereas 16% of peasants belong to large-scale land holders (farm size >100 ha) own 78% of total agriculture area (IBGE, 1998b). These figures show the persistence of a powerful traditional oligarchic structure which together with missing development programs are a strong impediment to social and technological innovation. Lack of development is illustrated here by just a few indicators: almost 85% of population is living in total poverty (<50% of minimum income), mean income in Tauá is approx. 25% of the Brazilian. On average 48% of the population were illiterate and an overall of only 55 tractors was counted in Tauá (PNUD 1998; IBGE 1998a). Therefore, traditionally, many people are forced to emigrate, and peaks have been particularly noticed after droughts. The number of the inhabitants of Tauá is in constant decline since the beginning of the 90es (1996: 50,258 inhabitants, 24,125 urban). Population density is below 10 inhabitants/km 2, especially in rural areas (IBGE 1998b). Due to the global climate change, extreme climatic events, especially droughts will be more likely to occur and accelerate degradation and emigration processes. 2 Vegetation ecological studies A vegetation ecological transect was established from the center of the semiarid backland depression at Tauá city up to the higher mountains ( Serra of São Joaquim ) to assess the relations between soils, vegetation and land use (Fig.2). It could be shown that there is a strong gradient of land use intensity: In remote mountain areas extensive extracting activities are predominating. The remnant natural vegetation is almost restricted to these areas with bad accessibility. Increasing precipitation is supporting a more humid Mata seca forest type that can be found in higher regions of surrounding Serras ( m). In the semiarid backland depression, the drought adapted Caatinga type is abundant. In the lower parts and in the vicinity of Fig. 2: Profile of vegetation unit types Municipality of Tauá 744

3 Fig. 3: Schematic overview of different thematic features according the working process phases settlements grazing impacts are more pronounced. Agriculture is limited to the deeper alluvial soils. Naturally, approx. 60% of the flora of the Caatinga are woody. Both the density and the height of the trunks can decrease significantly due to degradation effects. Sometimes only cactus species resist grazing and wood cutting. 2.1 Floristic comparison using the Sörensen-Index In combination with soil samples a floristic field survey was conducted along the transect. The floristic similarity of different landscape units was compared by means of the SÖRENSEN index (see Tab. 1). The SÖRENSEN index ranges between 0 and 1. Values close to 1 show a strong similarity between units. It could be shown that a strong correspondence exists between the landscape units I ( extensive pasture and subsistence agriculture ) and II ( tree and shrub Caatinga with bare soil ). As the intensity of land use in both units was very high, the selection pressure apparently led to homogenization of the surviving relics of the tree Caatinga. Unit III ( tree and shrub Caatinga with tree cactus) had no significant similarity to the first two units (coefficient < 0,5). A weak correspondence between unit IV ( secondary tree Caatinga ) and the other units could be observed. The difference of the mountain (III, IV) and the lowlands unit types (I, II) is also reflected by the index. 3 Approach of the Landscape Ecology working group The aim of the working group Landscape Ecology is to identify and to understand the specific processes leading to degradation in the Tauá region in order to define and promote adapted land use strategies. Therefore the dynamics of ecological and socio-economic processes need to be studied. Landscape features like vegetation, erosion, rivers, etc. reflect both the natural site conditions as well as the specific footprint of human activities in the landscape. The approach of the working group Landscape Ecology is based on both deductive ( top Tab. 1: Sörensen index values 745

4 Fig. 4: Aggregation phase - Slope classes, natural erosion risk, actual erosion susceptibility (from left to right). The respective valuation classes are increasing from light to dark. EDP: S. MÖRTL, Landscape Ecology, TU München Fig. 5: Land cover / Land use in the municipality of Tauá-CE down ) and inductive ( bottom up ) methods to detect these complex interrelations (see Fig. 3). Integrated models can relate physical and biotic features of natural sites to socio-economic features of the land use management system. The systematic correlation of these features within defined spatial units (i.e. landscape units) helps to detect patterns, that can be interpreted and evaluated for the whole region. The approach of the working group Landscape Ecology comprises four main working phases (s. Fig. 3): (1) Analysis phase: Assessment of natural resources and anthropogenic impacts to provide a basic geo-ecological data set. Literature and cartographic studies led to a series of thematic maps like geology, relief, hydro-climatology, phytoecology; (2) Aggregation phase: selection and linking of the most important parameters. A fine grained soil map (Secretary of agriculture of the State of Ceará) was digitized for the reference area of Tauá. A matrix considering erosion characteristics of these soil types on different slope classes led to a natural erosion risk map. The actual erosion susceptibility risk was defined by a further overlay with actual land cover units, which were valuated regarding their capability of erosion protection (see Fig. 4). (3) Integration phase: systematic integration of natural site and anthropogenic data to define geo-ecological units and to characterize degradation/desertification processes; By visual interpretation of satellite images (LANDSAT TM, bands 3, 4, and 5) (land use, see Fig. 5), the overlay of thematic maps and additional ground checks of reference 746

5 German-Brazilian Workshop on Neotropical Ecosystems Achievements and Prospects of Cooperative Research Tab. 2: Description of geo ecological units in the municipality of Tauá-CE Fig. 6: Geo-ecological units in the municipality of Tauá-CE 747

6 sites landscape units were delineated. The landscape units represent both characteristics of natural site conditions and land use management system (see table description in Tab. 2 and map in Fig. 6) (4) Application phase: land(scape) assessments and development of strategies for sustainable land use. 5 References IBGE - Fundação Instituto Brasileiro de Geografia e Estatística (1998a): "Censo Agropecuário , No 10. Piauí, Rio de Janeiro. IBGE - Fundação Instituto Brasileiro de Geografia e Estatística (1998b), Base de informações municipais (1996) [CD-ROM], Rio de Janeiro PNUD; IPEA; FJP; IBGE (1998), Desenvolvimento humano e condições de vida: Indicadores Brasileiros, Brasília 4 Perspectives of the Landscape Ecology working group Ceará The following topics have been defined for the next working phase of the Landscape Ecology working group of Ceará: Inventory of mineral resources of Tauá: environmental impact assessments of mining exploitation Further selection of pilot areas (transects) for vegetation and soil studies Study of correlations between soil types and potential vegetation Classification of degradation / desertification susceptibility Contribution of expert knowledge and data to the integration levels of WAVES, especially for the transfer of MOS- DEL (MOdel for Sustainable DEvelopment of Land Use) to the Tauá region. Landscape characteristics like topography, soil, vegetation, etc. will be analyzed basing spatially on small-scale watersheds. Correlations of land use management and natural site conditions will be investigated regarding erosion and degradation effects. 748

7 Editors Reinhard Lieberei 1, Helmut K. Bianchi 2, Vera Boehm 1, Christoph Reisdorff 1 1 Universität Hamburg, Institut für Angewandte Botanik, Ohnhorststr. 18, Hamburg, Germany 2 GKSS-Forschungszentrum Geesthacht GmbH, Max-Planck-Straße 1, Geesthacht Germany Layout Printing Helmut K. Bianchi, GKSS, Karsten Bittner, Documedia, Geesthacht, Germany GKSS-Forschungszentrum Geesthacht GmbH, Geesthacht, Germany ISBN X Lieberei, R., Bianchi, H-K., Boehm, V., Reisdorff, C., (eds.) 2002: Neotropical Ecosystems, Proceedings of the German-Brazilian Workshop, Hamburg GKSS-Geesthacht. The publishers give permission to copy single contributions from the Proceedings for personal use exclusively. Copies may be passed on only with the correct specification of the source. The research cooperation has been carried out under the auspices of the German - Brazilian Govemmental Agreement on the Cooperation in Scientific Research and Technological Development. The issuance of the Proceedings and the production of the CD-ROM was sponsored (Code ) by the Federal Ministry of Education and Research The responsibility for the contents of the contributions is solely the authors'.