6. Evaluation and monitoring

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Last update: June 2023 - How to cite


Transport infrastructure projects generate diverse impacts on habitats and species (see Chapter 1 – Ecological effects of infrastructure). European legislation and country specific regulations, require an assessment of these impacts on local biodiversity, and the design and application of mitigation measures to manage those impacts. These measures include actions to avoid, reduce or compensate for the impacts of any new infrastructure, and for enlargement and adaptation of existing infrastructure (see Chapter 3 – The mitigation hierarchy). Monitoring and evaluation comprises the activities needed to understand whether these measures have been effective in reducing impacts on biodiversity, and if not, apply corrective measures and verify whether these are working or not.

Main messages

  • Monitoring combines repeated observations and measurements taken over time, usually to assess the temporal change in a parameter either in response to a disturbance or intervention or to quantify the performance of a plan or project, measure, or action.
  • Evaluation aims to critically assess, test, and measure the design, implementation and results of a plan or project, in relation to its objectives.
  • Monitoring and evaluation have two main goals: i) assess the effectiveness of mitigation measures in reaching the goals for which they have been designed, and ii) measure the effects of the project on biodiversity conservation targets.
  • Research studies are a type of monitoring and evaluation that go beyond usual practice by conducting more advanced studies to assess the correlations or causality of an intervention or exposure on a population. These can provide invaluable insights into not only on what works and does not but also on why which is fundamental to apply corrective actions efficiently.
  • The monitoring plan should be designed, discussed, and approved within the Environmental Impact Assessment (EIA) and Strategic Environmental Assessment (SEA) process and will be different depending on the aim of monitoring. All monitoring plans should: establish a biodiversity baseline, define the monitoring parameters, delineate the monitoring area, identify habitats and species to be monitored, define a time frame as well as methods, schemes, and techniques to be used, and agree on the form and scope of the monitoring outputs.
  • Planning and preparing an appropriate monitoring plan takes place at the end of the initial Strategic Planning phase and throughout the successive phases of the project, from design, construction, and operation phases to decommissioning.
  • Establishing appropriate schemes, methods and techniques is fundamental to ensure comparability and replicability of monitoring activities.

Actions to take

  • Define clear objectives for monitoring and evaluation identifying which biodiversity elements and mitigation measures are the focus of monitoring.
  • Elaborate indicators, metrics, and tools to monitor the achievement of objectives.
  • Design clear and robust methods and techniques to ensure results are replicable and reliable.
  • Propose a sampling design and evaluate its feasibility within the available budget. If not feasible propose a new sampling design and/or method and re-evaluate feasibility.
  • Collect a robust baseline on natural habitats and species in the study area before project construction.
  • Follow clearly defined schemes, methods, and techniques to collect information in the study area about impacts on the biodiversity elements identified in the monitoring plan.
  • Apply adaptative management principles by changing mitigation measures when monitoring shows that mitigation objectives are not being met.

Gaps of knowledge and future research

  • There is little well documented available knowledge on the impacts of transport infrastructure on biodiversity over long term periods (more than 10 years after construction), especially on long-lived species demography and the genetic pool.
  • More research is needed on eco-ethology, or behavioural ecology. This is the study of what behaviour an animal adopts to maximise its chances of survival and reproduction in a given environment. This discipline can link the pressures created by infrastructure with the chances of survival of an animal population which can be important for mitigation design and ecological restoration.
  • Much progress has been made in recent years in modelling how the presence and distribution of species evolves over time. This modelling is most often based on machine learning with software capable of learning from sample data. However, further computer coding research is necessary to create efficient and robust algorithms.
  • The use of new technologies such as DNA surveys, image processing, bioacoustics or automatization of data collection, among others, have a huge potential to improve the efficiency and reduce the costs of biodiversity monitoring and evaluation.
  • The digital era brings a range of new techniques and approaches such as, for example, Building Information Modelling (BIM) or the use of sensors to manage risks of accidents, that can greatly improve the design of infrastructure and its subsequent monitoring and evaluation. 

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