Assessing ecosystem services - TESSA

IAM carbon transects team working at Sierra Bahoruco, Dominican Republic




The Toolkit for Ecosystem Service Site-based Assessment (TESSA) has been developed through a collaboration of six institutions with input generously provided by scientists and practitioners from multiple disciplines.  The toolkit provides accessible guidance on low-cost methods for how to evaluate the benefits people receive from nature at particular sites in order to generate information that can be used to influence decision making.

TESSA is primarily aimed at conservation practitioners, although the methods may be applicable to a wide range of users, including natural resource managers (e.g. forestry, fisheries, water managers), land-use planners, development organisations (e.g. for poverty alleviation), and the private sector.



The methods in the toolkit are designed to be applicable to users from developing and developed countries, and across all terrestrial and wetland habitats (currently excluding marine areas). The current version (1.2) provides methods for assessing global climate regulation, flood protection, water provision, water quality improvement, harvested wild goods, cultivated goods and nature-based recreation.


The toolkit includes:

  • An overview of ecosystem services, key concepts and caveats
  • Guidance on conducting a preliminary scoping appraisal for site(s)
  • Decision trees (flow charts) to lead the user to the most appropriate methods according to the characteristics of the site
  • Details provided for over 50 methods for assessing particular aspects of the ecosystem services listed above
  • The valuation of an ‘alternative state’ in order to compare a current and alternative state of the site and hence estimate the impact of potential or actual changes on the ecosystem services provided
  • Worked examples on how to derive a value (quantitative, including potentially economic, and/or qualitative) for each service, including presenting the difference in value between two states of the site
  • Guidance on how to synthesise the data for each service into a summary of ecosystem service change at site scale
  • Guidance on assessing how the benefits are spread across local, national and global communities
  • Advice on how to disaggregate the values at the local level into measures that reveal potential inequities in the costs borne and benefits received by different individuals

TESSA is an evolving resource, and more content will be added in future versions (subject to funding).


What the toolkit does and does not do


Does not

Help users who have limited capacity (technical knowledge, time) and resources (money, people) to measure ecosystem services

Assess all ecosystem services


Provide insights into the overall value of ecosystem services at sites, and a way of comparing the services provided by two states of the site

Provide total economic valuations (although monetary values can be calculated for some services)

Provide scientifically robust information on ecosystem services as a first step to guide practitioners on whether more detailed studies would be useful

Provide ecosystem service assessments that can be translated directly into Payment for Ecosystem Service (PES) schemes and Reducing Emissions from Deforestation and Forest Degradation (REDD+) projects

Indicate who will be the ‘winners’ and ‘losers’ as a result of any change in the state of a site and in associated ecosystem service delivery

Provide a ‘blueprint’ for assessments – it must be adapted to the local context

Help decision-makers appreciate the true value of nature, and the consequences of loss and degradation of natural habitats




Application in the field

The methods range from household surveys and participatory mapping to habitat surveys and the use of simple modelling software. The approach is relatively low cost compared with many other tools, and does not require advanced technical skills. However, understanding ecosystem services can be fairly technical and some relevant experience and/or training may be needed, e.g. from others who have used the toolkit, or have other experience of assessing ecosystem services.

The toolkit is designed to be used both online and in the field and is provided as a ‘user manual’ in a simple workbook structure. An interactive PDF is available to download on to a computer or other device (e.g. laptop, notebook, tablet) so that the methods and guidance can be accessed in remote locations.

The methods and approaches presented in the toolkit have been tested at 24 sites to date, in countries including Burundi, Cambodia, Cameroon, Dominican Republic, Ecuador, Fiji, Grand Cayman, Kenya, Malawi, Madagascar, Montserrat, Nepal, UK and Vietnam, across temperate and tropical forest and wetland habitats. To see the outputs of some of these studies, refer to the list of additional resources and publications below.


Contact details




The Toolkit for Ecosystem Service Site-based Assessment has been developed by









With additional financial support from