Glossary of Key Terms

This glossary provides definitions for key terms used throughout the Biodiversity & Infrastructure Handbook, supporting consistent understanding across disciplines such as ecology, engineering, transport planning and policy.

Definitions are based on legal texts, reference documents and expert agreement, and cover essential concepts related to wildlife and traffic, habitat fragmentation, ecological connectivity, mitigation measures, monitoring, green infrastructure and nature-based solutions. The glossary helps practitioners interpret technical guidance and supports clear communication between stakeholders involved in infrastructure projects.

If you are new to transport ecology or working in a multi-disciplinary team, the glossary can serve as a quick reference before exploring detailed handbook chapters. Terms will continue to evolve as the handbook is updated through expert collaboration and user feedback.

Last update: October 2023 – How to cite

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There are currently 18 names in this directory beginning with the letter M.
Major road
Road which is assigned permanent traffic priority over other roads.
Matrix
In landscape ecology, the background habitat or land use type in a mosaic, characterised by extensive cover and high connectivity. See also ‘Mosaic’.
Median
The strip of land separating the lanes of a dual carriegeway road or a motorway, which separates traffic flowing in opposite directions. Often vegetated with grass, shrubs and/or trees. Synonym: 'Central reservation'.
Metapopulation
A set of local populations within an area, where typically migration from one local population to at least some others is necessary to sustain local population numbers. The metapopulation may have a higher persistence than the single local populations.
Metric
A set of measurements that quantifies results.
Microhabitat
Small?scale differences in habitat.
Migration
The regular, usually seasonal, movement of all or part of an animal population to and from a given area. Usually undertaken by some species in response to changing seasons or climatic events, such as rainfall.
Minimise
See 'Reduction'.
Mitigation
Action to reduce the severity of, or eliminate, an adverse impact.
Mitigation hierarchy
A framework for managing risks and potential impacts related to biodiversity and ecosystem services. It includes the following hierarchical but iterative actions to manage impacts: Avoid, Reduce or Minimise, Restore, and Compensate. These are often described as the four steps on the mitigation hierarchy which can also be summarised in 3 steps: Avoid, Reduce, and Compensate, when restoration actions are included as part of reduction or compensation measures.
Mobile Remote Sensing (MRS)
Any kind of sensor mounted on a mobile vector. Mobile vectors can therefore be satellites, vehicles, aeroplanes, UAVs, etc. In practice, MRS is generally deployed for specific reasons and with a specific purpose.
Mode (of transport)
“Different ways of transporting people and goods (e.g. air, road, rail, maritime, inland waters, cycling, walking, etc.).”
Monitoring
A process driven by the evaluation goals that combines repeated observations and measurements taken over time, usually to assess the temporal change in a parameter or in response to a disturbance/intervention or to quantify the performance of a plan/project, measure or action against a set of predetermined indicators, criteria or objectives. In the framework of transport ecology, monitoring is a key tool which begins with the design of the monitoring programme.
Mosaic
The pattern of patches and corridors embedded in a matrix (in this case, within a landscape). See also ‘Matrix’.
Motorway
Road with dual carriageways and at least two lanes each way separated by a central reservation called ‘median’. All entrances and exits are signposted and all interchanges are grade separated.”
Multimodal
Pertaining to more than one 'mode' of transport.
Multiuse overpass
Structure built over transport infrastructure with multiple functions including the movement of fauna. It combines wildlife and human uses such as small forestry roads, cattle passages or pedestrian paths. Modifications are included to encourage use by wildlife such as addition of strips covered by natural materials and vegetation, and screens to reduce traffic disturbance when required. Combined with perimeter fencing that funnels the animals to the structure.
Multiuse underpass
Structure built under transport infrastructure with multiple functions including the movement of fauna. It combines wildlife and human uses such as small forestry roads, cattle or pedestrian passages. A drainage function including streams or other small waterways inside the structure is also compatible and may even lead fauna through the passage. These underpasses may include modifications to increase wildlife use such as fencing to funnel the animals, adaptation of vegetation at the entrances and measures to avoid excessive pooling of water. Combined with perimeter fencing that funnels the animals to the structure and with screens to reduce light and noise disturbance from traffic when required.