Much of the debate surrounding Britain's EU referendum has centered on immigration or the economy, but environmental groups have also weighed in on the upcoming vote that is gripping the nation.
On Thursday, U.K. voters will go to the polls to decide whether their country remains in or leaves the European Union (EU).
Here, CNBC takes a look at the issues surrounding the environment and speaks to organizations and experts about how a Brexit could impact both clean energy and nature.
Nature knows no borders
Dustin Benton, head of energy and resources at independent U.K. think tank and charity Green Alliance, told CNBC that the environmental case for staying in the EU was clear.
"European legislation has been critical to cleaning up the U.K.'s air and beaches, and preserving our habitats. Pollution and migrating wildlife cross borders, and so must our laws," he said.
"Even though Britain is an island, our low carbon future is linked to the rest of the EU's," Benton added.
"British diplomats have amplified the U.K.'s voice via the EU in international climate agreements, and our offshore wind sector will grow faster and be cheaper if we're well connected to our European neighbors, both physically and via markets with shared rules," he said.
As a member of the European Union, the U.K. is signed up to the Renewable Energy Directive, which requires the EU as a whole to "fulfil at least 20 percent of its total energy needs with renewables by 2020", according to the European Commission.
Each nation in the EU has set its own renewable targets. In addition, all EU countries have to make sure that a minimum of 10 percent of transport fuels are derived from renewable sources by 2020.
Unified voice
A host of big green organizations have come together to back Britain remaining in the EU.
One of the most high profile environmental organizations in Britain, WWF-U.K. focuses on the protection of rivers, wildlife, climate and oceans.
"Although there is room for improvement, the EU has been good for our wildlife and wild places. Beaches and rivers are cleaner, habitats have been protected and we are fighting climate change together," a spokesperson for WWF-U.K. told CNBC.
In its financial year ending on June 30, 2015, WWF-U.K. says it received £907,000 ($1.32 million) in funding from the European Union to, among other things, work on protecting our rivers and fight climate change.
Stating that the WWF was not commenting on the wider political and economic debate, and stressing that it was not telling people how they should vote, the spokesperson added that, "we have looked at the evidence on the environment and concluded that on balance, the safer option for our wildlife and environment is for the U.K. to remain within the EU."
While Friends of the Earth describes the Common Agriculture Policy as being "an environmental disaster," it adds that being in the EU has given Britain less air pollution, safer products, protected wildlife and cleaner drinking water and beaches.
In a paper on membership of the EU released last summer, the organization – which says that for the financial year of 2014-15, less than one percent of its funding came from the EU – stated that, "For the sake of our environment, we should remain part of the EU."
'Nature has been well served'
At the beginning of June, the chief executives of WWF-U.K. and the Royal Society for the Protection of Birds (RSPB) wrote a joint article in The Telegraph newspaper in which they said that, "the evidence shows that nature has been well served by our membership of the European Union."
The RSPB is the largest nature conservation charity in the U.K., and has also received funding from the EU for projects it is involved in.
"What we've said is that, on balance, based on the evidence that we've got and the challenges that we've issued to both sides … of the campaign, that it would be safer for nature to remain," Martin Harper, the RSPB's conservation director, told CNBC in a phone interview.
Giving one example of the positive impact European legislation had had, Harper – who also stressed that the RSPB was not telling people how to vote – said that the EU's Birds Directive and its Habitats Directive had both "helped to improve the populations of threatened species."
