Landscape Ecology, Connectivity and Fragmentation

Landscape Ecology

The natural environment is an extremely complex network, which functions as a framework of relationships between living beings and their environment. The advancement of human activity has resulted in a series of processes that can compromise the good development of these relationships. La landscape ecology is the scientific discipline that studies these relationships, between spatial patterns and ecological processes in a given area. In other words, he is interested in how natural and human elements interact in a landscape, forming a mosaic of interconnected ecosystems.

Landscape

In landscape ecology, the concept of scenery goes beyond the panoramic or aesthetic conception. In this discipline, it represents a heterogeneous spatial unit composed of a set of ecosystems that interact with each other. In other words, a landscape is a mosaic of different tiles or patches of different habitats (forests, rivers, fields, etc.) that are interconnected and that work as a complex system.

Ecological connectivity

In this regard, the concept of Ecological Connectivity, (or landscape connectivity). Ecological connectivity, beyond being a simple concept, is a fundamental reality for the survival and proper functioning of ecosystems. It could be defined as the capacity of a given landscape to allow the use of this space by different species. This capacity for use, determined by the capacity for mobility, is essential for organisms to search for food, find mates, disperse and colonize new territories.

We can imagine a landscape as a large game board. Each species is a piece that needs to move around the board to find food, reproduce, seek shelter or simply explore. Ecological connectivity is the extent to which these pieces can move freely and make use of between the different squares on the board.

In short, ecological connectivity is the extent to which the landscape allows species to use space effectively to carry out their life cycles.

One of the biggest threats faced by this delicate balance is the loss and fragmentation of habitats. This phenomenon, mainly the result of human activity, consists of the division of large areas of natural ecosystems into smaller and isolated fragments, which limits the movement of species and reduces their capacity to use the landscape. The processes responsible for this loss are multiple and difficult to separate (habitat loss, insularization caused by the reduction and progressive isolation of habitat fragments, edge effects, etc.).

Ecological fragmentation

La habitat loss: the first link in this chain. Habitat loss refers to the decline or disappearance of natural areas where diverse species of flora and fauna live. This phenomenon occurs mainly due to human activities such as deforestation, urbanization, intensive agriculture and pollution. Habitat fragmentation is, to a large extent, a consequence of the loss of natural habitats. By reducing the area of a habitat, the amount of resources available to the species that inhabit it decreases and their carrying capacity decreases.

But fragmentation is a process that goes beyond just the loss of habitats, because in this process, the spatial arrangement of the tiles must also be considered.

Tile or patch

Una Tile or patch In landscape ecology, it is a relatively homogeneous area within a landscape, with differentiating characteristics from adjacent areas and with defined boundaries. They are the basic components of the landscape, which define the structure of the landscape.

Así the ecological fragmentation It is a process that occurs when a habitat, such as a forest or a meadow, begins a process of “gruyerization” due to the loss of surface in the tiles, leaving empty areas or “holes” in the middle of a landscape that was previously continuous, which can lead to it being divided into smaller and more isolated fragments.

The main causes of fragmentation are human activities, related, on the one hand, as has already been indicated by the loss of habitats itself (for example, deforestation, the cutting of trees to obtain wood, but also the substitution for agriculture, grazing or other uses, which reduce the extent of forest uses and divides them into smaller fragments).

But on the other hand, other activities such as urbanization and the implementation of infrastructures such as roads, railroad lines, power lines, which fragment natural habitats, where the habitat loss factor is less important than others such as Barrier effect.

Barrier effect

It is a phenomenon that occurs when a structure or environmental condition prevents or hinders the movement of organisms between different areas of a habitat. These barriers can be physical, such as roads, rivers or fences, or ecological, such as sudden changes in the type of vegetation or environmental conditions (for example noise, weather conditions...), based in this case on the behavior of organisms, being a barrier that could be defined as ethological.

This is probably one of the best-known ecological impacts of linear transport infrastructures. Infrastructures limit the movement of taxons through habitats, more or less intensely depending on their specific characteristics (on a road, for example, width, permeability, traffic intensity or the existence of passages for fauna are important) and the characteristics of organisms (such as habitat requirements, dispersion capacity, mobility, etc.).

In the most drastic cases, infrastructures constitute an insurmountable barrier for species and establish partial or total isolation between populations, causing very little or no genetic exchange and leading to inbreeding processes.

Consequences of fragmentation

Finally, the effects of all these processes of habitat loss, fragmentation and barrier effect would be:

• Loss of biodiversity: Smaller fragments cannot support large and diverse populations of species.
• Isolation of populations: An increase in the distance between the fragments, leading to a greater difficulty in connecting these fragments
• Alteration of ecological processes: Fragmentation can interrupt processes such as pollination, seed dispersion and nutrient cycles.
• Increased edge effect: there is an increase in the perimeter/surface ratio and, consequently, a greater exposure of the fragmented habitat to matrix interference, increasing the edge effect and worsening the quality of the habitat.

Border effect

The decrease in the size of the fragments is associated with an inevitable increase in the perimeter/surface ratio. This creates on all the tiles a perimeter band of habitat with adverse conditions for many of the species, thus producing a zoning with a low-quality edge habitat and a higher-quality indoor habitat.

The loss of habitat quality in the perimeter area is caused by greater interaction with neighboring tiles, being an inevitable effect of fragmentation processes, with serious consequences for the survival of affected populations.

All of these effects generally produce a progressive reduction in population sizes in each of the habitat tiles. In short, the reduction, fragmentation and deterioration of the habitat end up causing an atomization of the original distributions in increasingly smaller and isolated subpopulations, subject to increasing genetic and demographic viability problems, which can negatively affect other parameters such as body condition, reproductive effort (Allee effect), stability during development, behavior, etc...

To mitigate the negative effects of fragmentation, it is essential to carry out ecological restoration processes and in general, carry out actions to improve ecological connectivity. This can be achieved through various actions, such as minimizing habitat loss, habitat restoration degraded, the definition of ecological corridors or the implementation of defragmentation measures in infrastructure projects.

Conclusion

Habitat loss and fragmentation is one of the greatest threats to global biodiversity. Understanding these processes and their consequences is essential for developing effective ecosystem conservation and restoration strategies.

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