Our issues in The Netherlands are probably similar to Denmark's and the biggest issue is not all agriculture. Meat and milk production has an outweighed impact on destroying the environment. You need far more land to grow crops to feed livestock and keeping cows leads to a lot of nitrogen deposition.
We can reduce land use and have food security if people were not so intend on eating/drinking animal products every day (and there are perfectly fine vegetarian alternatives).
I believe the insistence on being a major agricultural producer in the EU despite having some of the largest population densities in the region has a lot to do with it.
A huge chunk of that output is purely for export.
That depends on how you define "perfectly fine". All of the vegetarian alternatives have a lower protein quality index, which matters if you're trying to get enough of the essential amino acid s without increasing calorie intake.