The importance of ecological connectivity or landscape connectivity

Land uses have changed throughout history due to different causes, both natural and anthropogenic causes. Therefore, we can assert that landscape is a dynamic element, but what exactly is landscape? It is defined as a heterogeneous and relatively large portion of the territory, composed of a mosaic of tiles (or patches) with different types of cover (habitats, ecosystems) that interact with each other. The minimum unit within the study of the landscape is the tile (or patch), which is a relatively homogeneous area, with relatively well-defined borders, and with characteristics different from the adjacent areas.

The effects of land use change can be adverse if they lead to the loss, degradation and fragmentation of habitats, leading to a significant decline in biodiversity and even the extinction of species.

The degradation of habitats, or ultimately their destruction, occurs when natural habitats are unable to maintain the species present, resulting in the displacement of their biodiversity to other places or their direct disappearance. On the other hand, fragmentation is a process by which a large area of habitat is transformed into a number of smaller tiles, separated from each other by other types of cover. In this way, there is a loss of physical continuity between the different parts of the original habitat. This fragmentation can generate negative effects such as a reduction in the size of the tiles, the isolation of tiles or the increase of the edge effect; although in some cases it can also generate positive effects such as increasing the heterogeneity of the landscape (diversity of roofs and habitats in the landscape).

For all these reasons, it is absolutely advisable to carry out a previous study of the landscape before undertaking changes in land use, to know the dynamics of the landscape and to minimize the possible impacts of such changes on land cover. This study can be carried out through the analysis of ecological connectivity or landscape connectivity, which is the degree to which the territory facilitates the movements of species (individuals and genes) between different tiles and resources of the habitat.

The analysis of ecological connectivity is of enormous importance in landscape management, conservation and environmental impact assessment. There are several methodologies and analysis tools, which vary in complexity and data requirements, but the most operational, adaptable, flexible and efficient in terms of the amount of data required and level of detail in analysis and results is to analyze the connectivity of the landscape as if it were a graph.

A graph is the graphical representation of a network. According to the RAE, they are diagrams that represent objects (landscape tiles) using dots and the relationships between these objects (pairs of elements) using lines. Points are represented as vertices (also called nodes) and the relationships between them are represented by edges. The image represents the tiles of the habitats in black and the connections between tiles with red lines.

Thus, through the graphic representation of the landscape through degree theory, and taking into account the movement or potential movement of species between landscape tiles, we can generate an idea of the dynamics of the landscape.

In Environmental Ideas we value the impact that land use change can generate on landscape connectivity due to the loss and fragmentation of habitats, taking into account the dynamics of the landscape.

Bibliography

• Calabrese JM, Fagan WF. 2004. A comparison-shopper's guide to connectivity metrics. Front Ecol Environ. 2 (10): 529-536.
• Course “Tools for the analysis of ecological connectivity: concepts, methods and examples of application”, taught by Professor Santiago Saura Martínez de Toda.
• Saura S, Martín-Queller E, Hunter Jr. LH. 2014. Forest landscape change and biodiversity conservation. In: Azevedo JC et al (eds.) Forest Landscapes and Global Change: Challenges for Research and Management. Springer Science+Business Media New York.