The green and white colors symbolize “the pure air and the green land”. The oval with a line through the middle is a stylized symbol combining the initial letters in the words “environment” and “organism”. This stylized symbol also resembles the Greek letter “theta” which is associated with the Greek word “thanatos” (death). This symbol, therefore, implies mankind’s threat to the environment.
This flag is one of a number of Ecology Flags developed in the United States in the late 1960s and early 1970s. The first such flag was simply the Stars and Stripes with its blue replaced by dark green and its red by light green. That design, made by the Paramount Flag Company of San Francisco in August 1967, flew at the famous People’s Park incident at the University of California in Berkeley. The colors symbolized “the pure air and green land tha was America once and that can be ours again if we take the action necessary to recover our heritage.”
On 25 October 1969 political cartoonist Ron Cobb developed a symbol for the ecological movement based on an oval and circle and on the initial letters of the words environment and organism. The resulting design, which he put in the public domain, resembled the Greek letter theta. Look magazine (21 April 1970) widely popularized the theta symbol, which it associated with the Greek word thanatos (death) in light of human threats to the environment and atmosphere of the earth.
Look incorporated the theta – in chartreuse (later often rendered as yellow or white) – in a flag with green and white horizontal stripes and a green canton. Other variations were subsequently developed, but Look’s “Ecology Flag” remains the most popular design expressing environmental concerns.
The Flag Bulletin, No. 155 – The Flag Research Center