It looks plenty believable. Though the writing could use some improvement (it gets convoluted around all those 'but's and 'while's), my only real concern is that these two sections contradict each other:
'The Surface is toxic, but not because of the atmosphere, but because of the pollen of the various plants are toxic. The air is often filled with it especially in vegetation populated locations. Wind storms kick up this pollen, making the surface almost impossible to inhabit safely without life support systems.'
'While the atmosphere is perfectly breathable, the massive trees let off pollen and spores that are toxic to most foreign life forms. While this is a hazard, there are locations on the planet that are safe. Near the shores, the poles, or under ground, the spores are very rarely ever found in these locations.'
The first section says it's almost impossible to find safety, the second says it's not very difficult.