I am currently working on an alien planet which is inhabited by a race that is millions of years more advanced than us. (They have utopian like cities, cure to all sorts of disease, interstellar travel, superior nanotechnology etc.) Their species though has never start a singe war, conflict or crime within their civilization and they have never resorted into destroying their ecosystem or driving other species into extinction for their own purposes. But my question is, could a species become so advanced without a single problem on its planet?
Although I am uncertain whether such an instinct is plausible (totally lacking aggression and not wanting to change the environment seems the "loosers evolutionary strategy" to humans), after they are there and intelligence is achieved, they can advance.
They see technology as a way to keep the environment in better shape.
As they start to overpopulate their planet, they realize that either they have to violate the environment - to obtain resources for their life - or violate each other - to take resources from each other, institute forced birth control, etc... Therefore they choose the third way, advancing out into the space. So it is not that there are no environmental problems on the planet, rather than that they react quickly, aptly and cooperatively to them, and they form a motivation to further development.
If the sapient species evolved late in the lifespan of its parent star. For example, a F5 or F6 star will leave the main sequence on the timescale it would take intelligence to evolve. The aliens could need to create space travel for their survival. To establish habitats in space, on other planets and moons, and even exoplanets. Their need for interplanetary and interstellar travel can simply arise from their to survive as a species.
Any sapient species that has had technology and civilization for millions of years will ready move into space if their survival is at stake. Also, any technological civilization will need for satellites and space vehicles for communications, scientific research and exploration, and gaining access to resources in asteroids and the other planets of their planetary systems.
Attempting to 'live in peace with their environment' doesn't automatically imply 'without a single problem'. If their environment was sufficiently hostile to them and the problems were sufficiently difficult to fix, they could plausibly have the impetus to develop space travel. Once they are exposed to new conditions like other solar systems and possibly hostile alien races, the rest of their technological development would follow from there
The most obvious example is if they came to the realisation that their local star was going to go supernova soon. For something a bit less dramatic, if their planet of origin is exposed to frequent solar flares from its local star, the aliens would be faced with the near constant threat of bursts of lethal/crippling radiation. The desire to escape such conditions would be readily understandable. Tectonic instability, or unpredictable and extreme weather patterns could do the trick as well.