It could throw off biological clocks in the animal kingdom:
The biggest worry in this sphere is annual rhythms in mating, birth, migration and hybernation which have evolved to associate any given day length with the climatic conditions that usually accompany it at that latitude. Day length is a kind of short-hand that many species use to determine how best to time their annual activities, and once the month of March no longer means an average temperature of 12 degrees or whatever, the disconnect can be very stressful on a species. There are also animals that depend on synchronizing their annual rhythms with those of their food source. If their timing is thrown off, they starve.