Septic systems are affected by their distance away from the root systems of trees. The further away the better. Roots are incredible in their ability to find moisture and nutrients in their surrounding environment. They have the ability to infiltrate the smallest of surface blemishes, then expand and break through to their food supply. Wooden, concrete and plastic septic tanks are all fair game, as is their discharge into the leach field. Unfortunately the only way to deal with encroachment is to remove the trees and their root bundle.
Photo-voltaic (PV) solar panels are tremendously impacted by shading. For any day, peak power production can be expected for only 4-6 hours around high noon when the sun is at the optimum angle, when it is perpendicular to the angle of the solar panels. If the solar system was installed 10-15 years ago, most likely it was suitable for the location. However on a heavily wooded lot, trees can double in height over that same period of time, producing shade on the south facing solar panels, where there was none when they were originally installed. If the solar panels cannot be relocated, then tree topping is necessary.
Finally tree trunks and branches do break during wind storms. Or worse, they can completely topple over. If the fall line is in the direction and over the cottage, then there is no limit to what damage can inflicted on the building structure. Prevention measures may require a combination of selective tree removal and tree-topping.
Remember that if the property is over 20 years old, the landscaping was very different from what it looks like today and the (over) growth may never have been anticipated.
Any vacation property purchase needs to consider the cost of managing mature landscaping and trees in particular. As much as you may be in love with the trees, some may have to go in order to improve view lines, reduce shading and cut back exuberant overgrowth.