By Catherine Weller, senior lawyer with environmental lawyers ClientEarth

The bulk of environmental legislation in Scotland and across the UK is derived from EU directives.

The Scottish Government is responsible for the national laws to reflect these directives, but the legislation itself stems from 1972 European Communities Act.

When we leave the EU this Act will be repealed and the national legislation will therefore also fall away.

These EU laws provide major protections for animals and plants, and their habitats - both onshore and offshore - clean beaches and air quality – to name just a few.

The Prime Minister has promised that all existing EU derived legislation will be incorporated into UK law. Officials on both sides of the border face a huge task to make this work.

Brexit leaves a huge question mark over our green laws.

There’s uncertainty because the government says legislation will only be kept “where practical.” That is hardly a full blown guarantee that all environmental legislation will be retained on the statute books.

Indeed, Andrea Leadsom, UK Secretary of State for the Environment, has said that only two-thirds of environmental legislation will be directly retained by the Great Repeal Bill. This puts the UK’s environmental laws – and therefore the UK’s environment – at risk due to the gaps and the regulatory uncertainty.

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Furthermore, if devolved administrations take different approaches to different pieces of EU law, then overall protection for the environment will suffer due to its trans-boundary nature.

The risk of potential differences either side of the border is exacerbated by the fact that Theresa May has stated that there will be an opportunity to scrutinise, amend, repeal or improve legislation in future.

There is a suspicion that certain EU laws, where the government has struggled with compliance in the past, might be first in the firing line. The administrations could undermine protections by taking different approaches and tackling different questions at different times.

The EU Birds and Habitats Directives form the cornerstone of wildlife and nature protection across the UK, and they provide the framework for the largest network of protected areas in the world – through the Natura 2000 sites. These ensure the long term survival of threatened species and habitats. What will happen to those laws in future?

The Department for Environment, Food and Rural Affairs announced earlier this year that they would publish a 25 year plan for the environment. Following the referendum result clearly this has become an even bigger undertaking. The detail – and therefore the impacts – this will have on UK nature is still unclear.

Brexit poses a serious threat to the current legislative framework governing air quality. The government has been breaching those laws since they were introduced in 2010 and has been dragging its heels over measures to achieve compliance ever since. Given that, might ministers want to weaken those laws once we leave the EU?

Fortunately, in the short term we are in a good position because ClientEarth won its legal challenge against the UK government in the High Court earlier this month – for the second time in two years - and we are due back in court again on Monday, for a hearing on what actions the government must take to comply with the law. It’s not just UK ministers at fault - the Scottish Government has also failed to take significant action on air quality.

Glasgow and Edinburgh are among the UK cities which have illegal levels of pollution.

So, in order to protect people’s health, a proper air quality plan with a UK wide network of clean air zones must be put in place immediately.

In the longer term, Brexit reinforces the need for a new Clean Air Act, to enshrine obligations currently enjoyed under EU law as a bare minimum, but also to significantly improve on EU legislation, including:

• Setting stricter obligations as recommended by World Health Organisation guidelines;

• Clarifying roles and responsibilities of various tiers of government and devolved administrations;

• Fully implementing the Aarhus Convention, thereby guaranteeing rights of access to information, public participation and access to the courts where air pollution laws are broken;

• Filling the enforcement gap left by the European Commission.