

Trees in Santa Monica. (Photo by bloodyeyeballs via the LAist Featured Photos pool on Flickr)

The drought has changed much of the terrain in L.A., and one of those changes is happening with our trees. Thousands of trees are dead or dying in the Castaic Lake State Recreation Area. In Elysian Park, the dryness has accelerate the aging process of the trees, turning the area into what the L.A. Times described as "a zombie forest."

As such, the need to count the street trees in L.A. is an urgent one (the last time we’d done this was over two decades ago). This led the the L.A. Bureau of Street Services to call up researchers at Caltech for help. And now those researchers are asking Google for assistance, reports the Times.

Pietro Perona, a Caltech professor who specializes in making computers recognize objects, has developed a method in which he uses computers to identify and count trees using images from Google Earth and Google Street View. Whereas it may take dozens of humans several months to name and count all the street trees in L.A. (which might cost $3 million to do), Perona said that his method could do it "overnight."

It's not quite as simple as it sounds, however. First, Perona has to render tree images into geometric algorithms to train a computer to recognize the different types of trees. From there, the task is a two-tier process. Computers will use the overhead view from Google Earth to look for shapes and shades that indicate the location of trees. The computer then takes down the latitudes and longitudes of these locations. Using these location markers, the computer goes into street view, takes a closer look at the trees, and identifies them.

Perona tried out his method in Pasadena and, when compared to city records, it was found that his results were 80% accurate.

The plan sounds like it could be a good one. But there's an issue: While Google lets researchers to use their library of files, their terms don't allow cities to use them for official purposes. The city has been negotiating with Google for two months on the matter.

What's the importance of tree counting? As noted before, the drought has left a devastating mark that can reverberate for decades, and we need figures on trees to measure the total impact. It will also help inform officials in matters of city planning. Greg Good, Mayor Eric Garcetti's executive officer for city services, told the Times that, "It's important to understand where the gaps are in terms of canopy. We want to use this inventory to identify storm water capture opportunities, ameliorate urban heat island impacts."

According to the Bureau of Street Services, there over 10 million trees growing in L.A., with 700,000 street trees that are growing along 6,700 miles.