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."