Print this page


Archive for November, 2006

The Hippocratic Oath of Land Management

For a while now when I give talks about managing invasive plants, I bring up the subject of the Hippocratic Oath of Land Management: First Do No Harm.

We should choose methods of conducting our work that have the least negative impact—or fewest unanticipated consequences—on the land and habitats we manage.

It means, for example, avoiding unintended disturbance in removing invasive plants since other invasive plants may take advantage of that disturbance.

It means not compacting soil or creating ruts by driving across a wet field, even if it means walking some distance carrying the equipment. It means being thoughtful and aware of the impact of every action. We need to pay attention to the possibility of unintended changes of species composition, hydrology, geomorphology, forest stucture, nutrient availability, etc.

I had thought that applying the medical analogy of the Hippocratic Oath to land management was a unique idea, until I read the cover story in the October – December issue of Conservation In Practice. Entitled "Do No Harm" the article is by Mark Jerome Walters (29-34).

It’s mainly about how efforts to save the endangered Hawaii raven actually hampered the species’ recovery. "The lure of technology seems to tip the balance toward always ‘doing something’ rather than erring on the side of doing nothing to minimize the risk of harm" (34). Without the knowlege of how to study the birds without frightening them, researchers disrupted nesting and reproduction. Walters has written a book about what happened: Seeking the Sacred Raven: Politics and Extinction on a Hawaiian Island (Island Press, 2006).

[I call this inability to study something without affecting it (you guessed it!) the "Heisenberg Uncertainty Principle of Nature Study"—based on the quantum physics wave-particle conundrum. Although this is not a proper description of the actual Heisenberg Uncertainty Principle (see the Wikipedia entry) it is worth keeping in mind that researchers often do affect their study subjects.]

I don’t mean to imply that we shouldn’t study nature or manage our preserves, only that we need to be aware that the things we do may have unanticipated consenquences. And of course, we can’t ever anticipate all of the unintended outcomes of our management.

There are also limitations to the medical analogy of the Hippocratic Oath. An ecosystem is not as static as a human body, for example. What we see today, what we take for granted as what a place is, is only a snapshot of a dynamic, ever-changing web of relationships among a changing cast of characters.

Our Third Responsibility

I often remind the people who work here—summer interns, preserve assistants, or volunteers—that getting the job done is our third most important responsibility in land management.

Working safely, and ensuring the safety of others is our first responsibility.

Protecting the equipment is job #2. Since we share equipment, making sure the tools aren’t damaged is also a safety issue. Equipment and the training to use it safely is also an investment in our ability to get the job done.

So completing the task at hand, while very important, ranks third.

What I like most about this job…

This holiday weekend, aside from Thanksgiving Day itself, was filled with warm sunny days perfect for a walk on the preserve and many people took advantage of the fine weather. I had several pleasurable meetings with preserve visitors who were kind in expressing their thanks for our work protecting the land.

More than anything I enjoy sharing the preserve with others.

Tree Hugger

I suppose after writing a post about cutting down hazard trees (see below) I should affirm that I prefer my trees "on the hoof"—that is, standing, growing, shading, in the full majesty and grace of their size, slow and persistent growth and beauty.

There is a satisfaction that comes from a skilled job well done when I remove a hazard tree but one has to respect the years that it took to grow this creature. We remove a few: damaged, dead or decayed—and a threat to a target—while we protect the vast majority of others…

No Bobcat Yet

I recently took a "busman’s holiday" of sorts.  I spent several days with some friends at their cabin in North-central Pennsylvania.  We did a lot of wildlife watching. 

One day I was sitting on a stump in a patch of open woods.  My friend walked in to join me and spooked a flock of turkeys.  They began flapping wings and flying all around me.  In fact, I thought a couple were going to slam into me as they tried to get their heavy bodies airborne.  I got a great look at their breast feathers.

Some of the other wildlife I saw were pileated woodpeckers, golden-crowned kinglets, and nuthatches.  Ravens were spotted each day wheeling in the wind and croaking.  Barred owls were heard at night. 

I didn’t see a bobcat however.  My friends see them on their property often, but I have yet to see one.  I have seen two of the three North American cats in the wild, but never a bobcat.  (Actually, I should probably include jaguars and ocelots to make it five species.)  I once had a lynx only ten feet away from me in northern Quebec.  And I once watched a mountain lion stalking prey from only 40 yards away in Colorado.  Both sightings allowed me to see these animals in their natural environment with no awareness that a human was nearby.  They are truly marvelous creatures, sinew and fur. 

You would think that bobcats should be fairly easy for me to see, considering there is a large and growing population in Pennsylvania.  They may even visit Mariton from time to time, although I have yet to find any sign of them.  So, I will keep hoping that someday a bobcat crosses my trail.

Hazard Tree Work

TreeworkAt Natural Lands Trust we have a hazard tree management program overseen by Tom Kershner, arborist and manager of Gwynedd Wildlife Preserve. Each of us monitors potentially hazard trees on the preserves, consulting with Tom as needed. We each received training from Bill Graham at Morris Arboretum on evaluating defects; we also have a few books and Forest Service publications on the subject.

A hazard tree is defined as a tree that has both a defect and a target. The defect could be a cavity of rotted wood or some other sign of potential failure. Or the tree could be dead, something that happens to all trees someday and which results in its eventual return to earth.

But the tree must also have a target to be designated hazardous. Standing dead trees in the forest are good wildlife trees, providing dens for animals and insects for birds, and we leave them for the habitat they create. But a dead tree that might fall in the road is a problem.

So each hazard tree is rated 1 – 4 and each target is rated 1 – 3 (for example, a bench is a much higher target than a trail; public roads are all #3’s). We remove all seven’s and sixes and evaulate fives case-by-case. Some fives and fours we leave standing but monitor twice each year.

I keep track of the hazard trees I monitor in a database. It tells me that we have removed 49 trees (from a couple miles of road frontage) at Crow’s Nest in the last ten years. (There were a few other small ones that did not warrant the paperwork.)

Some trees I take down myself. Other that pose a greater challenge Tom helps me with. And those near wires we hire a full-time arborist to prune or remove (see photo above).

Going into this year we had only six trees I was monitoring, down from 30 a few years ago. But nine trees were found newly dead this year along Hopewell Road, and all of them made the list. For most of them I think it was the natural process of forest maturing that killed them—there isn’t room or resources for every tree to make it to full size. But all of them were near the telephone wires and Hopewell Road, so we hired local arborist Norm Koontz of Chesapeake Tree Care, who used his bucket truck to reach over the wires and remove the hazards.

Some of the removed trees are left in the woods to rot and return nutrients to the forest. Where there isn’t enough room for that we cut some up for firewood and if necessary chip the branches for mulch for the trails. We’ve even gotten a few beams for the barn from sound wood in these trees. And when a storm comes there is less cleanup because we have already removed some of what might have fallen.

Recent Happenings

Sunrise_1Last week, for perhaps only the second time, I saw a woodcock (Scolopax minor) at the preserve. I was walking around the preserve with easement monitors from Brandywine Conservancy, and we flushed the bird from brush along the trail.

Saturday night we held a successful Star Stories event: a dinner followed by the myths of the constellations’ origins and a walk to look at stars. The skies were a bit cloudy, but we had a good night hike. And the wonderful parents and kids pulled off a series of skits illustrating the legends of the constellations.

You might think the flower blooming season is over, but the fall witchhazel (Hamamelis virginiana) is just starting to flower.

I hiked the penultimate section of Denise’s Appalachian Trail hike on Sunday; now she has just 5.2 miles left, out of the approximately 2,160 total (she knows just how many the actual figure is this year). We completed a section that is very close to home that she had skipped earlier in the hike: from PA 183 to Port Clinton. I have hiked about 10% of the trail, most of that this year. She hasn’t had time to update her online trail journal recently, but she will. She will finish the trail on the day after Thanksgiving!

Got Goulashes?

I don’t need to tell anyone that it rained A LOT yesterday.  At Mariton, we received 2.35 inches of rain in about 24 hours.  Consider that the average for the entire month of November is 3.37 inches, and you will realize how big a rain event that was. 

This morning, the TV weather folk announced that the Pineapple Express will be delivering a series of low pressure areas to the Northwest (U.S.), which will then cross the county to our area.  They forecast some rain every 2 -4 days, or sometime mid-week and then again sometime during the weekend.  Get your boots ready.

Even though I spent most of the day in the office, I did get out on the trails for a couple hours.  Because most of our trails go up the hill, heavy rains can cause a lot of erosion.  I like to check the trails during heavy rains to find the areas that need attention.  We have installed water bars on a lot of the trails.  In fact, Boy Scouts have been very important in installing and replacing waterbars over the years at Mariton.  I was pleased that very little water was running on the trails.  In addition to the waterbars, the thick layer of leaves on the ground were holding the water and releasing it slowly. 

Farming at Crow’s Nest

FarmingWe lease 172 acres of Crow’s Nest to a local farmer, Frank Hartung, who has farmed this land for many years, as his father Ken did before him. He plants a conventional rotation of field corn, soybeans, winter wheat, winter rye, and hay.

The farming is done following a Conservation Plan prepared by the Natural Resource Conservation Service (NRCS), a cooperative project of the Federal government and Chester County. The crops are laid out in strips that are parallel to the contours of the terrain, so that soil does not wash away down a row, and so that no more than 100 feet wide of slope is in a single crop. Seasonally dormant crops such as corn alternate with winter-growing crops such as winter wheat, for example, so that erosion in one strip is stopped by the next.

The field corn is usually harvested by combine. The kernels are loaded onto a truck for animal feed, and the stalks are chopped and left on the land as a mulch to reduce erosion and return organic matter to the soil. (In a drought year when corn ear production was severely reduced, some stalks were harvested instead for sileage, another kind of animal feed.)

The soybeans are also harvested by combine, as in this photo, which also shows the crop strips. Winter wheat and rye are cool-season crops that are planted in the fall and harvested in the spring when they mature and set seed. The seeds are stripped off, again as a grain for food, while the hollow stems are baled for straw and used for animal bedding.

Hay is a perennial crop, largely alfalfa, that is grown in one place and harvested for several years by cutting in late June and perhaps again in August. The cut grasses are left to dry in the sun for a couple days, then twirled into windrows and baled. Hay is used as the fiber in large animal feed.

Frank works cooperatively with other farmers in the neighborhood, sharing specialty equipment and storage space.

Big Tree

Bigtree_2The kids at WebWalkers yesterday nominated a tuliptree (Liriodendron tulipifera) at Crow’s Nest to be included on the list of Big Trees in Pennsylvania.

Our tree is certainly not the tallest, and doesn’t score as highly as some others on the list, but it is pretty close! The trees are scored on a combination of circumference of the trunk at 4.5 feet above the ground, the height, and the average spread of the crown.

You can see this tuliptree on the path from the parking lot to the visitor center barn.


  • expand2017 (34)
  • expand2016 (141)
  • expand2015 (167)
  • expand2014 (197)
  • expand2013 (192)
  • expand2012 (241)
  • expand2011 (244)
  • expand2010 (223)
  • expand2009 (233)
  • expand2008 (201)
  • expand2007 (227)
  • expand2006 (269)
  • expand2005 (187)
  • expand2004 (5)