Is Gardening Green?

There are some aspects of gardening philosophy that I really wrestle with, and one of them is ecological impact.  There are a lot of good reasons why I believe that people should grow their own food, but I'm not sure that the saving the Earth is one of them.

Growing my own food does allow me to reduce the amount of food transported to me over great distances.  Also, my garden is mostly free of pesticides and totally free of herbicides.  When I do use pesticides I follow the instructions to the letter, and time my applications so as to minimize the threat to beneficials and pollinators.  (Many insecticides are only harmful to these creatures during the time it takes them to dry after being applied, so they should be applied in the early morning on a bright, sunny day.  After that they must be ingested - by an insect actually eating the plant - to kill.) 

However, there are a lot of good reasons to question the environmental benefits of growing your own food:

1. Excess packaging and shipping associated with any product purchased for use in the garden: tools, seeds, fertilizers, soil amendments
2. Environmental damage due to the production of these materials (I'm thinking of things like rock phosphate, chemical fertilizers, peat...)
3. Excess water use above what would be required in large-scale agricultural production
4. Damage to the soil due to improper/unskilled management (here I'm thinking about the fact that most farmers no longer till their land, while most gardeners still do, resulting in loss of topsoil and the disruption of the natural soil food web)
5. Loss of natural environment due to the extra land required for my inefficient (relative to professional agriculture) gardening
6. Extra energy required to store food produced in a seasonal climate for year-round consumption vs. transporting it from more temperate areas

It strikes me that even the most knowledgable and conscientious food-growing projects I've heard of rely on the import of - at minimum - lots of organic material from the surrounding area.  Many of them could not function in the absence of conventional agriculture.  Or they could, but would need to devote considerable land to the sole purpose of producing biomass to add to their food-producing soil.

What do you think?  Is gardening green?  Do the environmental benefits outweigh the drawbacks?