This year's US Open course has cut down 15,000 trees in the last 25 years and Oakmont is now barely recognizable

Andrew Redington/Getty Images

Much is being made about the difficulty of this year's U.S. Open which is being held at one of the toughest courses in the United States, Oakmont Country Club.

While there are plenty of reasons Phil Mickelson has called Oakmont "is the hardest golf course we've ever played," one aspect of the course is flying a bit under the radar: just how much the course has changed over the last couple of decades.

The biggest change is the number of trees. While there are still trees along the outer border of the course, Oakmont has removed 15,000 trees from the interior of the course since the U.S. Open was held here in 1983. About half of the trees were removed prior to the 2007 U.S. Open at Oakmont and the other half have been removed since, according to John Zimmers, Oakmont's course superintendent, during a recent interview with Golf Course Management magazine.

In fact, after the purge, there is now just one tree remaining on the interior of the course, near the tee at hole No. 3.

YouTube/USGA

The rest of the course looks markedly different.

Here is a look at the fairway of the par-4 No. 4, as seen back in 1983. This is looking back at the fairway from the green. You can see that trees line both sides of the fairway. The Church Pew bunker is difficult to see, but it is near the top of the image.

YouTube/Dana Starbuck

Here is the same hole this year. There are trees beyond the hole, which is the boundary of the course, but nothing short of the green.

YouTube/USGA

Here is the approach at No. 7 in 1983. Again, trees everywhere.

YouTube/Dana Starbuck

And here is the same approach at No. 7 in 2016. It is not even the same course.

YuoTube/USGA

Finally, here is the fairway at No. 14, a hole where only the tee is near the exterior border of the course.

YouTube/Dana Starbuck

And No. 14 this year. This is the reverse angle, looking towards the green. But again, no trees on the fairway or near the hole.

YouTube/USGA

The tree removal was spurned by a desire to get the course back to what it looked like when it was first designed by H.C Fownes in 1903 and gives Oakmont a more aesthetic appeal.

"The views you get now are just astonishing," Zimmers told Golf Course Management magazine. "It reveals this beautiful piece of land and really shows off the architecture. Now, you can see everything. This is visionary."

There is still the issue of lopping off 15,000 trees. While the idea can be a bit cringe-worthy for many, there is some upside, environmentally, according to Zimmers.

"Frost burns off faster," Zimmers said, noting that water usage at the course is down 45%. "If it rains, it dries faster. We need less water, less fertilizers. Overall, there's no question it's better for everybody."