On the one hand... 
So, I'm worrying about global warming, biodiversity loss, pollution, resource depletion, and other intractable, global problems, and I feel I have to do something about it. Because of this, I am thinking about an environmental career. Whether it´s project management for energy efficiency programmes, engineering renewable energy technology, marketing for an eco products company, academic research, journalism, or even the holy grail of environmental careers - government and policy, many of these are based in offices.

...on the other...
But surely a true environmental career, is, by definition, based in the natural environment, for example farming, wood working, arboriculture, conservation or being a hiking or climbing guide. Jobs in the natural environment are not powerful jobs, are not based in cities, are generally not managerial, and do not reach out to people or industries whose behaviour we feel need to change. The jobs that give the most freedom - self employment or even self-sufficiency - do not even allow people to work within a large organisation. So there appears to be a conflict between changing the world and the my love of nature; true environmental careers involve renouncing power and influence in multiple ways.

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My first motivation was probably my love of nature, with the plight of future generations something I have learned to care about as my global awareness deepened. On some level, I remember some moments of authentic experience, where I discovered what my body was designed for. My innate "biophilia", or love of nature, was awakened with a rush of endorphines as you saw, smelled and heared a living environment, as the elements - sun, wind and rain - beat against my skin, as I walked, worked, climbed, ran and generally acted like the animal I am, and dwelled in forests, moutains and on the sea. On some level I felt small, connected, part of a greater whole. 

There appears to be a conflict between changing others and being fulfilled myself, but perhaps there is not. If I live a life that denies my need for the nature inside and outside of myself, I am unlikely to truly inspire anyone, I am merely helping to perpetuate the system that causes everyone to do the same. When I think of the people who have inspired me, it is the people who have had the guts to do what they really want, tree surgery, setting up camp in the mountains to work towards self sufficiency, or travelling between farming communities for years. I do worry that if environmentalism requires people to live a somewhat alternative way, how will it ever become mainstream? There are many people doing excellent work in offices all over the world. But if the Executive Secretary of the UNFCCC, or the president of the US, can only achieve very limited success, what can I realistically achieve? Am I going to deny myself for my whole short life for questionable results that I will never be able to measure and which may not even appear in my lifetime?