Foray into tree-counting shows we're in a losing game

posted 08:23 PM 11/18
Link this article here.

As a forest ecologist, I fly over remote parts of the world to visit my study sites. Looking down on those vast unbroken forests of Alaska and Amazonia, trees seem a nearly infinite resource. But when my plane circles over the huge urban sprawls of Mexico City and Los Angeles, I am reminded of how much our species has affected the arboreal world.

Those images inspired me to learn how many trees exist in the world. NASA satellites and scientists have created maps of Earth from outer space. Because different types of trees reflect sunlight in particular patterns, we can assess the land area covered by different types of habitats, e.g., evergreen forests, savanna woodlands, even city parks.

The Food and Agriculture Organization in Rome provides information on the density of trees in each habitat. By multiplying the acreage by the density of each forest type, I estimated the number of trees on Earth today as 400,246,300,201. Human census data revealed that the world population is 456,789,877. By dividing the number of trees by the number of people, I had my bottom line: 61 trees per person.

Is this a lot or a little? Is it shrinking or expanding?

A colleague noted that the annual deforestation rate is 0.22 percent and that world population will pass the 8 billion mark in 2028. Thus, we are losing tree cover and gaining population. Calculating backward with these numbers to 1800, the number of trees per person then would have been 599 per person, nearly 10 times the current number. Projecting ahead, today's ratio of 61 will spiral down to 47 trees per person in 2030 and only 24 per person in 2200 if current trends continue.

How to put this in a historical perspective? Humans have deforested land with fire to create habitats favorable for hunting game for thousands of years. More recently, deforestation took place in Western Europe in 1300, largely because of making wooden ships for trade and naval warfare. Each of those ships required harvesting 6,000 mature oaks, with accompanying ecological damage such as flooding and silting. So shrinking of the tree ratio is not novel, but its diminution is happening at record rates.

Last week, National Public Radio ran a report on this topic, ending the episode with a hopeful spin. "If you think we are using up more than our 61-each allotment, you can always plant a few more. After all, trees are renewable." Many listeners thought the conclusion was falsely positive, pointing out that mature forests support unique species and complex functions. Creating plantations or planting random trees does little to help those forests. We must also reduce our patterns of consumption, a more demanding task.

This "humanitree" number, however, has inspired thinking about actions.

One respondent said, "The number made me feel that I am responsible for 61 trees."

Another wrote that she is now growing and giving away free trees on her San Juan Island farm.

A listener suggested that determining this ratio could stimulate reforestation at the national, regional and neighborhood levels, with prizes for the highest ratios.

This foray into tree-counting showed me that many people recognize the importance of trees for humans, and the necessity to keep the humanitree ratio as high as we can. Discussion and debate on the topic is a good place to start.

Dr. Nalini M. Nadkarni studies forest canopies as a member of the faculty at The Evergreen State College. A member of The Olympian's Board of Contributors, she can be reached at nadkarnn@evergreen.edu.

Opening academia to families, civilians new trend in science

posted 06:40 PM 08/26

Last month, I flew to Milwaukee for the annual meeting of the Ecological Society of America. As with professional meetings in other fields, it presented an intensive immersion into the esoteric aspects of our tribe. Historically, it has comprised reports of science on remarkably narrow topics discussed in nearly pure scientific jargon.

Networks, spider webs: making the invisible visible

posted 06:48 AM 06/04

Years ago, I met Jonathan Coddington, a tropical biologist who studies the evolutionary biology of web-building in spiders. His fieldwork involved slowly inching his way through the rainforest understory on his hands and knees. He carried a poofer — a rubber bulb like the atomizer of a perfume bottle attached to a small pouch filled with cornstarch.