The effects on the estuary are highly localized and the gas releases aren t all that large compared to other sources, so it s probably better to save the estuary. But where methane was only 25 X better than CO2 at trapping heat, N2O is about 300 X better than CO2. Third, it is the major loss of N from the ecosystem. If it weren t for denitrification, ecosystems would accumulate N because of biological N fixation and human inputs, and N wouldn t be so limiting to organism growth in ecosystems. Uplifted sediments begin the weathering process to form soil and P is leached into riverwater to start the cycle all over.
Fluxes are large due to internal cycling.
Compared to C,N,S, humans do not have a large impact on the global P cycle.