As an interdisciplinary field, Landscape Ecology has developed theory and concepts with foundations in many other schools of thought. Broadly, there are two ‘traditions’ of thought in Landscape Ecology: a European tradition emphasising the long and pervasive history of human culture in shaping landscapes versus a North American tradition emphasising quantitative analysis of spatial patterns and ecological processes. Yet in both there is an interest in the reciprocal influences within landscapes between structures – such as spatial patterns of vegetation – and functions – such as ecological processes. As Forman and Godron put it in their classic Landscape Ecology text (from 1986):
"An endless feedback loop:
Past functioning has produced today’s structure;
Today’s structure produces today’s functioning;
Today’s functioning will produce future structure.”
There are numerous books and papers devoted to the theory and concepts of Landscape Ecology (see further reading below). Indeed, members of ialeUK developed a list of 20 concepts by which to classify the more than 900 contributions to the first 25 years of ialeUK conferences. Here, we present a shorter (if not simpler!) list, in which several of those concepts overlap (and note that some issues – such as spatial analysis and modelling – are covered on the Methods & Tools page).
Landscapes as Mosaics
One prominent conceptual model for understanding landscapes presents them as mosaics – patterns of juxtaposed landscape elements. These elements include discrete ‘patches’ of habitat sitting withing a non-habitat ‘matrix’, potentially connected by linear ‘corridors’. Known as the Patch-Corridor-Matrix model, habitat in this model is defined based on the needs of a specific organism.
Landscape elements (like patches) can be conceived of having clear ‘edges’ that discretely delineate habitat from non-habitat, or otherwise can be thought of as having ‘core habitat’ vs ‘edge habitat’. While some species, such as the Common Chiffchaff may prefer ‘core habitat’ in forest and woodland interiors away from the edge of patches, other species such as the Spotted Flycatcher prefer living at the edges of forest and woodland patches for the benefit of multiple resources provided by patches of different types (see Dolman et al. for a thorough treatment of woodland birds in patchy landscapes).
In reality, boundaries are not usually discrete and there are gradients of high to low quality habitat across space, but different conceptualisations of landscape elements can be useful in different circumstances. Thus, landscape ecologists are not interested in simply asking only about the composition of different land cover or land use types (how much?) but also about the spatial configuration of those land covers or land uses (where is located?). The spatial arrangement and structure of constituent units is important if we are to comprehend the landscape as a functioning whole.
Connectivity and Fragmentation
Most fundamentally, connectivity is about how readily organisms can move through a landscape. Landscapes with high connectivity (for a given species) are those that readily facilitate movement of organisms. Facilitation might be due to patches that are relatively close together (because of their configuration) or due to areas of non-habitat being relatively ‘permeable’ (because they are easy to move through). For example, amphibian species living in ponds and lakes (i.e. aquatic habitat patches in a terrestrial matrix) are known to find open fields and urban areas less permeable than forested land. Roads and highways also present barriers to movement – even for the persistent hedgehog – and thus reduce connectivity. Contemporary studies use tools such as circuitscape to incorporate connectivity assessments into Environmental Impact Assessments, to identify potential ‘pinch-points’ in landscapes that are particularly vulnerable to development impacts. Although the notion of organisms moving through an inhospitable matrix between islands of habitat has driven understanding of connectivity, less binary perspectives of landscapes are important for many species. Thus, practitioners and researchers are encouraged to be aware that measures of ‘connectivity’ are not absolute but relative depending on the species of interest and therefore are encouraged to be aware of the empirical evidence available for the particular species they are concerned with.
Closely related to connectivity, habitat fragmentation is a process of landscape change in which large areas of habitat are broken up into smaller discrete patches. Importantly, habitat fragmentation is explicitly spatial and not only about the total amount of habitat lost (although that is often a key factor). Rather, for a landscape ecologist, fragmentation is important because it changes the number of patches (usually increased), the average patch size (usually decreased), the ratio of ‘core’ habitat to ‘edge’ habitat in the landscape (usually decreased) and the isolation of patches (usually increased). Thus, fragmentation is often linked to the conceptually useful but largely theoretical SLOSS debate – is biodiversity conservation best facilitated by a Single Large Or Several Small patches of habitat?
Landscape Scale
Scale is vitally important for understanding landscapes. Most fundamentally, what counts as habitat or a discrete landscape unit depends on the scale of perception and mobility (thereby ensuring access to resources). Whereas for a beetle a habitat patch might be vegetation one tenth of a square metre in area, for a deer it would be more like one tenth of a square kilometre. And thus, the extent of the beetle’s landscape (10s of square metres) will differ hugely to that of the deer (10s square kilometres). For humans, on the ground our landscape is visual and maybe defined as what we could walk in a day. Observing from space via satellite remote sensing and the digital mosaics they produce, what landscape units and patterns we can detect (whether individual trees or large patches of forest) will depend on the spatial resolution of the sensor - the area of ground represented by each pixel of the digital image. One final key concept to note here: ‘landscape scale’ - what we have just been discussing - is not the same as ‘landscape level’. Landscape ‘level’ refers to a position in a hierarchically organized ecological system, for example below the biome level but above the patch-level. Scale has length units, level does not.
Social and Cultural Landscapes
Few landscapes are now untouched by human activity, and ignoring the role of humans in understanding ecological patterns and processes is increasingly untenable in human-dominated landscapes. Land use and land cover change is heavily influenced by socio-economic processes, and the historical impacts on landscape ecological processes is a key area of research. Even when land cover or configuration is not changing, understanding the impacts of management practices on ecological processes is key. Forman and Godron’s endless feedback loop means that ignoring the historic role of human activity is equally perilous in regions with very long histories of human activity. Cultural landscapes have been studied less in landscape ecology, partly because the cultural patterns are difficult to measure and partly because studying them requires skills and techniques not so well aligned to ecology’s quantitative and objective approach. But landscape ecologists – like Naveh and Antrop – have stressed the importance of understanding landscape holistically, including how cultural practices generate, inhibit, drive and constrain patterns and processes in the landscape. The sub-discipline of Landscape Character Assessment (LCA) goes some way towards incorporating a cultural element into landscape ecology.
Management and Conservation
In the 2020s, one of the primary motivators for management and conservation is a goal of the Kunming-Montreal Global Biodiversity Framework to conserve 30% of Earth’s surface. The UK government has committed to 30by30 – protecting 30% of the UK’s land by 2030 – but presents this as a bottom-up approach led by actors on the ground. Landscape Ecology can offer insights and tools to support the collaborative and cross-sector approach that is needed. For example, the concepts of connectivity and fragmentation outlined above are central to the idea of connecting wildlife-rich places to restore entire ecosystems to deliver the Nature Recovery Network at scale. The benefits of a landscape perspective for management are not limited only to biodiversity, but also other ecosystem services. For example, returning to the diagram above, aquatic environments need to be managed for water quality and flood control as well as for habitats, and here the composition and configuration of land use and cover within a catchment have a key role to play. Thinking about the landscape as a mosaic of components that may have important and differing effects at varying scales, and the existence of which are influenced by social and cultural values, exemplifies the roles that concepts and theories from landscape ecology can play in environmental management and conservation.
Text
James Millington and ialeUK (2024) CC BY-NC
Images
Stream Corridor Restoration: Principles, Processes, and Practices by the Federal Interagency Stream Restoration Working Group (FISRWG); Caitlin Lewis/ialeUK (2023) CC BY-SA; James Millington/ialeUK (2020) CC BY-SA
References and Further Reading
Dolman, P. M., Hinsley, S. A., Bellamy, P. E., & Watts, K. (2007). Woodland birds in patchy landscapes: the evidence base for strategic networks. Ibis. 149 146-160. https://doi.org/10.1111/j.1474-919X.2007.00748.x
Forman R.T.T. and Godron, M. (1986) Landscape ecology. Wiley.
Francis, R.A. and Antrop, M. (2022) A brief history and overview of landscape ecology In: Francis et al. (Eds.) The Routledge Handbook of Landscape Ecology. Abingdon: Routledge, 1-22.
Gergel, S. and Turner, M.G. (2017) Learning landscape ecology: a practical guide to concepts and techniques. [pdf freely available online]
Millington, J.D.A. (2022) Scale and hierarchy in landscape ecology In: Francis et al. (Eds.) The Routledge Handbook of Landscape Ecology. Abingdon: Routledge, 49-66.
Nassauer, J.I. (1995) Culture and changing landscape structure. Landscape Ecology 10(4):229–237
Naveh, Z. (1995) Interactions of landscapes and cultures. Landscape and Urban Planning 32:43–54
Wiens, J.A., et al. (2007) Foundation Papers in Landscape Ecology. Colombia University Press.
Wiens, J.A. and Milne, B.T. (1989) Scaling of ‘landscapes’ in landscape ecology, or, landscape ecology from a beetle's perspective. Landscape Ecology 3, 87–96 . https://doi.org/10.1007/BF00131172
Wu, J. (2010) Landscape of culture and culture of landscape: does landscape ecology need culture?. Landscape Ecology 25, 1147–1150 . https://doi.org/10.1007/s10980-010-9524
Wu, J. and Hobbs, R. J. (Eds.) (2007) Key Topics in Landscape Ecology. Cambridge University Press