Why do I do this?

I've been telling the story about cleaning up the river for a couple of years now, but I've never attempted to explain why, because primarily I want people to understand the problem, but more importantly, feel as though they can do something about it themselves. My motivations didn't seem to matter, but lately it seems like a question I ask of myself.
The exercise I get from kayaking helps me cope with the stress of work and being a single dad (nothing worthwhile is easy). But I think most importantly paddling is a very serene, almost meditative activity for me - even if I'm covered with trash. Just the sound of the paddle in the water and the sounds of nature makes me remember I'm part of a much larger picture. There are things that existed long before this lifetime and will be here long after my lifetime ends. That somehow makes my daily stress and challenges seem not so great after all. But it's more than just my favorite activity.
I've always had a deep connection to nature, it was clear even as a child. I'm not sure if it's because I'm told I have some Native American heritage or some other cause, but it's always been there. Seeing trash in a river or in a park or even along the roadside is a constant reminder to me that simply by living, especially in a western culture, I'm creating a burden on the planet every day. I feel bad about that.
In daily life, I recycle like crazy, have compact fluorescent bulbs throughout my house, and take the train to work, but I know I'm nowhere near carbon-neutral. If I could afford to switch my home over to geo and solar, I would, If I could haul the stuff away from the river in an electric car, I would, but I need a small pickup truck for that. If I had the time to grow my own food I'd even consider that. Cleaning up the river is not so much about doing something good, I'm trying to make up for the negative impact I have without even realizing it most of the time.
Don't get me wrong, it does make me feel good, and especially if I can inspire someone else to start thinking about their impact. While it gives an immediate feeling of accomplishment, the river provides a constant reminder that everything is impermanent. The constant change, the constant presence of a new problem brings awareness that what you've done is not important, what you're doing - now that's important.