How do the carbon, nitrogen, hydrologic, and phosphorus cycles get from organisms back to the environment?
Simple answer: through life processes such as respiration, elimination of body wastes, and death of organisms that return C, N, H2O and P to the environment.
All organisms are naturally a part of these 4 cycles, and as such return or revert some compounds to the environment due to daily life processes such as respiration, photosynthesis, excretion of wastes, etc. In addition, once an organism dies, its remains return to the environment in some form- dead leaves, dead tree or mouse in woods, etc. The nutrients C, N, H2O and P that were inside these organisms is returned to the environment for others to use (or locked up for years if no other creatures use them).