The regulation of junkyards in areas adjacent to any state highway included in the national system of interstate and primary highways is hereby declared to be in the public interest and necessary to promote the public safety, health, welfare, convenience, and enjoyment of public travel, to protect the public investment in public highways, to preserve and enhance the scenic beauty of lands bordering on such highways, and to promote the conservation of our natural mineral resources by encouraging the recycling of the reusable scrap iron and metals. The Legislature hereby finds and declares that junkyards which do not conform to the requirements of this division are a public nuisance.