Thursday, December 11, 2008

Oops, we already have a tree problem

Sad news. Our American urban tree population is in serious decline, and has been for several decades.

Source: 10 most magnificent trees in the world (Worth a look!)

Although several cities have started re-planting programs (Chicago & Los Angeles, for example), the trend of city tree cover has been steadily down. Tree cover in cities in Michigan and North Carolina are only 27% of what they once were, while Philadelphia and Chicago are only 16%. There are several reasons for the decline:
  • Sprawl. Cities and suburbs have expanded to accomodate growing population and appetite for larger houses with yards. Developers tend to mow down large, mature trees and later replant baby trees as accents for the houses.

  • Maturity. A large proportion of the trees were planted immediately after WWII, in a swell of optimism and civic pride. That was 60 years ago, and many trees are reaching their natural lifespan.

  • Tree injuries. Trees in urban areas are subjected to living with pavement over most of their root systems, mower injuries, and excavation and compactment of their roots. They also have to deal with greater pollution than their country counterparts. Urban trees are usually heavily stressed.

  • Attrition. Trees die from all sorts of reasons - weather, increased pest population, etc, and cities have tended to replant smaller, easier to maintain trees.

  • McMansions. Many consumers now prefer "no-lot line" and generally bigger houses, which don't leave room for the larger trees.

Urban trees are important for many reasons. They exhale oxygen, help prevent flooding and soil erosion, and provide shade and windbreaks. The shade keeps cities cooler. For example, in Atlanta, where 380,000 acres of trees were bulldozed over 25 years, the temperature in the city has risen 5 - 8 degrees Fahrenheit, compared to the countryside. This heat island effect can have drastic impact on human health during heat waves, which may increase in severity with global warming.

Trees also absorb carbon dioxide and particulate pollution. Street trees reduce the level of particulates by up to 60%. Large trees can take several decades to mature, but when they do, they absorb 60-70 times as much pollution as small trees. If we cut down trees to provide wood for fuel, we are putting ourselves in double trouble: creating particulate pollution while also destroying the way to absorb that pollution.

So we are entering a period of energy decline, where there will be increasing incentives to cut down trees for cooking and heating fuel, and our urban tree cover is already at historic lows in many cities.

But don't give up hope. After all, if they can replant Kenya.....


Clifford J. Wirth, Ph.D. said...

Yes, we have a lot of problems.

Independent studies conclude that global crude oil production will now decline from 74 million barrels per day to 60 million barrels per day by 2015. During the same time, demand will increase. Oil supplies will be even tighter for the U.S. As oil producing nations consume more and more oil domestically they will export less and less. Because demand is high in China, India, the Middle East, and other oil producing nations, once global oil production begins to decline, demand will always be higher than supply. And since the U.S. represents one fourth of global oil demand, whatever oil we conserve will be consumed elsewhere. Thus, conservation in the U.S. will not slow oil depletion rates significantly.

Alternatives will not even begin to fill the gap. And most alternatives yield electric power, but we need liquid fuels for tractors/combines, 18 wheel trucks, trains, ships, and mining equipment. The independent scientists of the Energy Watch Group conclude in a 2007 report titled: “Peak Oil Could Trigger Meltdown of Society:”

"By 2020, and even more by 2030, global oil supply will be dramatically lower. This will create a supply gap which can hardly be closed by growing contributions from other fossil, nuclear or alternative energy sources in this time frame."

With increasing costs for gasoline and diesel, along with declining taxes and declining gasoline tax revenues, states and local governments will eventually have to cut staff and curtail highway maintenance. Eventually, gasoline stations will close, and state and local highway workers won’t be able to get to work. We are facing the collapse of the highways that depend on diesel and gasoline powered trucks for bridge maintenance, culvert cleaning to avoid road washouts, snow plowing, and roadbed and surface repair. When the highways fail, so will the power grid, as highways carry the parts, large transformers, steel for pylons, and high tension cables from great distances. With the highways out, there will be no food coming from far away, and without the power grid virtually nothing modern works, including home heating, pumping of gasoline and diesel, airports, communications, and automated building systems.

This is documented in a free 48 page report that can be downloaded, website posted, distributed, and emailed:

I used to live in NH-USA, but moved to a sustainable place. Anyone interested in relocating to a nice, pretty, sustainable area with a good climate and good soil? Email: clifford dot wirth at yahoo dot com or give me a phone call which operates here as my old USA-NH number 603-668-4207.

Kiashu said...

Then you will just have to plant some yourself!

Of course, guerilla gardening is illegal, but it would be a pretty funny thing to be arrested for, I don't think you'd become the black sheep of the family for it :)