Quick history lesson: After the war, with Prussia in 1864, Denmark lost about 33% of it's area. That part was some of the most suited to agriculture. To compensate for those loses Denmark started a process of turning previously unusable land in to farmland. So lakes where drained, the the moors were drained, areas with sandy soil, good for nothing but growing common heather, was heavily fertilised and forests where cut down. There where even suggestion to drain parts of the sea between Denmark and Sweden.

In some sense it was good, and basically help shape modern Denmark, but it's just not needed anymore, and has come at the cost of wildlife, native plants and sea creatures. It didn't start out like that, but when you add modern intensive farming on top of killing of most of your nature areas, then things starts to go very wrong. Denmark has almost nothing of it's original nature left.