bulwark vs conservation

bulwark

noun
  • A defense or safeguard. 

  • A defensive wall or rampart. 

  • A breakwater. 

  • Any means of defence or security. 

  • The planking or plating along the sides of a nautical vessel above her gunwale that reduces the likelihood of seas washing over the gunwales and people being washed overboard. 

verb
  • To fortify something with a wall or rampart. 

  • To provide protection of defense for something. 

conservation

noun
  • The act of preserving, guarding, or protecting; the keeping (of a thing) in a safe or entire state; preservation. 

  • The discipline concerned with protection of biodiversity, the environment, and natural resources 

  • The protection and care of cultural heritage, including artwork and architecture, as well as historical and archaeological artifacts 

  • Wise use of natural resources. 

  • Genes and associated characteristics of biological organisms that are unchanged by evolution, for example similar or identical nucleic acid sequences or proteins in different species descended from a common ancestor 

  • lack of change in a measurable property of an isolated physical system (conservation of energy, mass, momentum, electric charge, subatomic particles, and fundamental symmetries) 

How often have the words bulwark and conservation occurred in a corpus of books? (source: Google Ngram Viewer )