Goddess worship has been practiced for centuries. The pagans; or the people who lived far from the protection of the castle walls (and subsequent tortures of the Crusades and the Inquisition) were simply referred to as pagans, not for their religious beliefs but because of their location. Mother Earth as Gaia was honored long before people even built castles; ruins of the temples can still be seen in parts of the world today.
It is an erroneous conclusion that everyone who does not practice Western religions and Christianity is a pagan and therefore a witch. While the words heretic and pagan often are used today to describe those who belong to the Wicca practices and faith, it is not as hard and thick a line some would have one believe.
Gaia Goddess is the earth. She is not a deity wherein she is inaccessible or lives high in the heavens. Gaia is earth, simple as that. You can access her simply by digging in your garden for the day.
When early tribes of hunter gathers settled down and began to produce what we know today as agriculture, they were superstitious and had little understanding of how the weather worked. As a result, a good crop was the result of sacrifices of grain and animals to the earth mother. The earth was revered and honored because that was were the food grew from, where the water ran through, and how the animals grazed. It is the source of all life, and because it "Bears" all of these things, it would only make sense that a believer sought her out as a female.
By the way, even though the word Gaia is Greek in its origin and means earth, there is no Greek Goddess Gaia. Gaia was simply the name given to the terra firma that the Greeks stood on. Gaia is the mother of all things living, and the Greeks, as we know, had a different deity for each of the elements, earth, water, fire, air, and a myriad of other needs and superstitions.
Today Gaia faith, or mother earth practices, is a huge part of the neopagan movement, which is on the increase ever since the seventies, or as soon as someone figured out that humans were wasting all of their natural resources. Practitioners of neopagan faiths believe at least to some degree, that natural disasters such as floods, hurricanes, and eruptions are Gaia's "Gentle" (compared to the force that she could use) reminder that we are on the brink of extinction as a race because of our selfish and controlling greed for the mother's resources.
Mother Earth as Gaia followers believe that we are the earth stewards, or caretakers of the mother earth and it is our responsibility to leave every area of land better than when we found it, or at least keep the disturbances to a minimum. In return, Gaia provides herbs for us to use as medicine, plants to eat, trees for shade, and every other thing we need to live. We owe it to mother earth to put hers and our energy to good use.