Star Trek: Nautilus
Qo’noS (or Kronos in english) is the Klingon Homeworld and the capital world of the Klingon Empire. Qo’noS is home to the Klingon High Council and other important institutions.
In 2293, the ozone layer on Qo’noS was severely damaged when Praxis, a key energy-production facility for the Klingon Empire, exploded after an accident involving over-mining, its destruction sending out a subspace shock wave. This event forced planning for the evacuation of Qo’noS and led to the signing of the First Khitomer Accord with the Federation.
Chancellor Azetbur refused to accept that Qo’nos needed to be abandoned. She instituted a two-fold plan to colonize more worlds with the Qo’nos population and to repair the ozone layer of the planet. The Klingon Empire lacked the advanced terraforming technology required to implement this plan. Chancellor Azetbor made a sweeping and unpopular alliance with the Federation in exchange for the technology to save Qo’nos.
By 2334 twelve new worlds have been colonized, reducing Qo’noS’s population significantly and to sustainable levels. In addition Federation atmospheric processors have extended the life support of Qo’nos by 100 years. Continued advances in technology and planet wide environmental regulations on Qo’noS make it seem likely Qo’nos is on its way to a full recovery in the next 50 years.