February

World Wetlands Day 02-02: February 2

March

International Day Of Action for Rivers 03-14: March 14
World Sparrow Day 03-20: March 20
World Water Day 03-22: March 22

April

Earth Day 04-22: April 22
Arbor Day 04: Last Friday in April

May

Green Up Day 05: first Saturday of May in Vermont
International Migratory Bird Day 05-03: May 3
Greenery Day 05-04: May 4 in Japan (previously April 29)
International Day for Biological Diversity (World Biodiversity Day) 05-22: May 22
Europarc European day of parks 05-24: May 24
Bike-to-Work Day 05: Third Friday in May

June

World Environment Day 06-05: June 5
World Oceans Day 06-08: June 8
Global Wind Day 06-15: June 15
World Day to Combat Desertification and Drought 06-17: June 17

July

World Population Day 07-11: July 11
International Tiger Day 07-29: July 29

September

International Day for the Preservation of the Ozone Layer 09-16: September 16
World Water Monitoring Day 09-18: September 18
Zero Emissions Day 09-21: September 21
Car Free Day 09-22: September 22
Ecological Debt Day (Earth Overshoot Day) 09-23: September 23 in 2008, but receding
World Rivers Day 09: every last Sunday in September

October

World Habitat Day 10: first Monday in October
International Day for Natural Disaster Reduction 10: second Wednesday in October
World Planting Day 10-22: October 22
International Day of Climate Action 10-24: October 24

November

International Day for Preventing the Exploitation of the Environment in War and Armed Conflict 11-06: November 6

December

World Soil Day 12-05: December 5
International Mountain Day 12-11: December 11