If you're planning to develop a site in the UK that contains trees or woodland, it's important to understand when a BS5837:2012 tree survey is needed. This standard, which was first published in 2005 and updated in 2012, outlines the guidelines for assessing trees and woodlands in relation to construction and development projects.

Here are some situations when a BS5837:2012 tree survey is typically required:

Planning applications: If you're submitting a planning application for a development project, you'll need to provide a tree survey as part of your application. This is to ensure that any proposed development will not adversely affect the trees on the site or surrounding areas.
Site appraisals: A BS5837:2012 tree survey may also be required as part of a site appraisal or feasibility study. This will help to identify any constraints that may affect the development of the site, such as the presence of protected or valuable trees.
Pre-purchase assessments: If you're considering purchasing a site that contains trees or woodland, a tree survey may be necessary to assess the condition and value of the trees. This will help you to make an informed decision about the potential of the site and any costs associated with managing the trees.

In summary, a BS5837:2012 tree survey is needed in situations where there are trees or woodland present on a site that is undergoing development or construction. It's important to engage a qualified tree consultant to conduct the survey and provide expert advice on the best course of action to take to protect the trees and ensure compliance with relevant regulations.