Landscapes Forest and Global Change - ESA - Escola Superior ...

T. Höbinger et al. 2010. Impact of changing cultivation systems on the landscape structure of La Gamba
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rice production sharply decreased while the oil palm industry is on the rise. During the last
decade many agricultural areas have been rapidly converted into oil palm plantations which are
already the second most area consuming land use type after pastures. The cultivation of oil
palms is increasing globally, causing severe problems in many tropical agricultural systems and
leading to deforestation, loss of biodiversity, destruction of soils and alteration of traditional
countryside (Fitzherbert et al. 2008). Until now in La Gamba new oil palm plantations are
mainly replacing former rice fields or pastures and there has not been much deforestation.
Nevertheless, this development profoundly affects the economic situation of La Gamba and has
strong influence on the landscape structure (Höbinger 2010).
Landscape metrics are a useful too to analyze and monitor changes in landscape pattern and
differences between landscapes (Uuemaa et al. 2009). Landscape structure mirrors a wide range
of ecological patterns and processes (Turner 2001). Several authors wrote about the use and
misuse of landscape metrics (e.g. Li and Wu 2004) and tried to figure out appropriable sets of
metrics for different scales and scientific questions (e.g. O’Neill et al. 1988; McGarigal and
Marks 1995; Botequilha Leitão et al. 2006; Cushman et al. 2008). A careful choice of metrics is
essential to avoid redundancies and misleading results (McGarigal and Marks 1995; Schindler
et al. 2008; 2009).
This study analysis the landscape pattern of the La Gamba area, and deviates ecological
consequences of ongoing land use change. It shall form a basis for further investigations and
action plans for biodiversity conservation in the area and other tropical landscape mosaics.
2. Methodology
2.1 Study area and land cover mapping
The study area, the village La Gamba and surrounding forest areas, is situated in the southwest
of Costa Rica (Golfo Dulce Region) and has an extend of 25.66 km² (8°41’ to 8°43’N and 83°9’
to 83°13’W). To investigate the landscape mosaic we mapped land cover and small-scale linear
landscape elements (see Figure 1). The base for the mapping of the region was a “QuickBird 2”
satellite image with a pixel size of 2.4 m for the multispectral channels (green, blue, red and
infrared) and 0.6 m for the panchromatic channel (La Gamba, Costa Rica, QuickBird scene
052017330010_01_P001, 6/12/2007 © Digital Globe (2008), Distributed by Euroimage).
To produce a vector map showing the land cover, we used the program ArcView® (ESRI, Inc.,
Redlands, CA) and defined eleven land cover categories: primary forest, secondary forest,
shrubland, riparian vegetation, fern-dominated vegetation, pastures, oil palm plantations, live
fences and timber plantations, agriculture, settlements and roads and drainage ditches and rivers
(including ponds). We used the statistics program R version 2.6.0 (R Development Core Team)
to illustrate the results in the form of barplots.
2.2 Landscape pattern analysis
To analyze the landscape pattern, the study area was divided into eight sections. All sections
should represent relatively homogenous and characteristic zones of the area and were delineated
in order to comprise mainly either forests or rural areas. Each section includes at least five of the
eleven land cover categories and is of compact shape (see Figure 1). Three of these sections
were summarized as “forest sections” (Bolsa forest, Station forest and Bonito forest), being
mainly covered by primary and secondary forest and five sections were summarized as “rural
sections” (Bolsa, Bonito 1, Bonito 2, La Gamba and Station agriculture), being dominated by
anthropogenic ecosystems (see Figure 1).
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.