A land of green fields for crop cultivation and cattle rearing limits the space available for the establishment of native wild species . Hedgerows , however , traditionally used for maintaining and demarcating land boundaries , act as a refuge for native wild flora . This ecosystem stretch across the countryside and act as a network of connections to preserve remnants of the ecosystem that once covered the island . Subsidies under the Common Agricultural Policy , which supported agricultural practices that preserved hedgerow environments , are undergoing reforms . The Common Agricultural Policy had in the past subsidised potentially destructive agricultural practices , for example by emphasising production without placing limits on indiscriminate use of fertilisers and pesticides ; but reforms have gradually decoupled subsidies from production levels and introduced environmental and other requirements .