Question
Marc

This question is regarding whether or not we should cut down a big leaf maple.  
We live in Seattle Wa. Our house sits on a bock which is fairly flat, however the yard drops off about 12 feet down to the street very steeply. There is a healthy 30 foot big leaf maple planted right into the drop off hillside. My wife believes the tree is pulling down the hill in front of our house and is contributing to the slow slide of the yard toward the street. I believe the tree is anchoring the hillside and slowing the slide creep. She wants to cut it down.

What are your thoughts?

William

Answer
Hi William.  According to the State of Washington Department of Ecology, the Big Leaf Maple (Acer macrophyllum) is excellent for shoreline erosion control. It is a large, fast-growing tree and needs plenty of space to grow. It thrives in poor gravelly soils and makes a massive root system on slopes, which makes it excellent for erosion control. It is a big tree, but also has correspondingly big and shallow root system, which makes it a poor choice near septic systems.

(http://www.ecy.wa.gov/programs/sea/pugetsound/species/maple.html)

According th Oregon State Univerity, the Bigleaf maple weighs about 47 lb/cubic foot when green, so a 30 foot tree is approaching 1-1/2 to 2 tons, depending on trunk diameter; About the weight of a full-size pickup truck.

Therefore, I doubt the tree is pulling the slope down with it. If your wife is still concerned about the slope migrating towards the neighbors, nothing beats a civil engineer's eyes on the problem. For your neighborhood, It may be a larger issue than one big tree, like subsidence or shallow fault-lines.  Evaluating the situation via the internet is not ideal.

Hope it helps (and sorry for the delay in responding) ~M