The currently observed changes to the Earth System are
unprecedented in human history. Efforts to slow the
rate or extent of change – including enhanced resource
efficiency and mitigation measures – have resulted in
moderate successes but have not succeeded in reversing
adverse environmental changes. Neither the scope of
these nor their speed has abated in the past five years.
As human pressures on the Earth System accelerate,
several critical global, regional and local thresholds
are close or have been exceeded. Once these have
been passed, abrupt and possibly irreversible changes
to the life-support functions of the planet are likely
to occur, with significant adverse implications for
human well-being. An example of an abrupt change at
a regional scale is the collapse of freshwater lake and
estuary ecosystems due to eutrophication; an abrupt
and irreversible example is the accelerated melting of
the Arctic ice-sheet, as well as glacial melt, due to an
amplification of global warming