You've raised some important issues, and as someone who’s also worried about fragile ecosystems and climate change, I personally appreciate your concern.
Let’s take a look at the source of your concern―the issues you list are not specific to farming that utilizes genetically engineered seeds, so a GMO label actually wouldn’t give you the information you’re looking for. All agricultural production methods, including organic, conventional and GM, affect the environment. Each system requires cleared land, pesticides, fertilizer, water and fuel and extracts soil nutrients. Importantly, though, good practitioners of each farming method (sometimes the same person uses all of them on a single farm) will work to mitigate the toll that agriculture takes on the land through judicious use of inputs; utilizing the least toxic substances; returning nutrients to the soil through cover crops; and incorporating no-till techniques to limit water runoff, reduce fuel usage and conserve carbon in the soil. Additionally, while the pollen of some plants can drift, whether they’re GM or organic, neighboring farmers work together to stagger planting times and establish buffer zones to avoid “contamination” of each other's crops.
Regardless, you're not alone in wanting a label that lists environmental impacts. In a November 2013 segment on NPR, “What's the Most Important Thing Food Labels Should Tell Us?,” four food experts were asked to describe their ideal food label. One of the experts wanted a label that would quantify the amount of deforestation and water and fertilizer usage for a food product. While environmental impact is not part of FDA’s mandatory product labeling system, in response to demand like yours, there are a growing number of private marketing standards and eco-labels for foods that are certified as “sustainable.” The standards for these different labels tend to vary, and I encourage you to do some research to see which type of label best addresses your particular issues.
Now I’m going to jump to “superweeds” but mostly pass the buck. We’ve had a number of great responses on our site about this issue, including this recent post by Jane Stautz, which also helps to explain why these “superweeds” are not a GMO-only problem.
Here is an excerpt:
“[W]hat is more likely happening with your so-called 'superweeds' is not so much mutation as it is a result of natural selection. That is, here and there as a result of natural diversity, a few weedy individuals at some given location already have a higher resistance than their peers to whatever method of weed control is in use. If those weeds then survive treatment and proliferate—and if you keep using the same weed control method over and over again―in time the only weeds left would be those that the method you’re using has difficulty managing. The way to break this cycle of natural selection pressure is to use multiple methods of weed control, including cultivation methods, and multiple modes of herbicidal action, so that no one weed with resistance to a specific means of control is able to use its resistance to its advantage…
“Any unvarying use of the same weed control method (whether chemical, mechanical or GM) is going to build natural selection pressure, allowing weeds to adapt. And that’s what happened with glyphosate-tolerant crops. Growers used the same game plan again and again over a period of 15 years because they had no other weed control option that they saw as offering them comparable value in terms of farm profitability and flexibility in operations.”
I will add one thing to provide some perspective on glyphosate-tolerant weeds with respect to other herbicide-resistant weeds. According to the Proceedings from the 2012 National Summit on Strategies to Manage Herbicide-Resistant Weeds, “there are 388 herbicide-resistant weed biotypes represented by 208 weed species. These evolved resistances include resistance to all of the commercially available herbicide mechanisms of action. One or more of these resistances may be represented in a given species. Over the last decade, resistance in (currently) 23 weed species has evolved to glyphosate, and the production of corn, cotton and soybean is threatened by the increasing numbers of glyphosate-resistant weeds in an increasing number of crop fields.”
Finally, yes, it’s absolutely your right to control how you spend your money, just as it is mine. And there are eco-labels already out there to help you make choices that support your principles. Again, though, sustainability is an agriculture-wide issue, and farmers, in general, work diligently to limit the negative impacts their specific production method has on the environment.