Monthly Archives: August 2013

Why Wolves Are Important

When discussing the conservation of wolves, it is important to understand why we should bother to save wolves from extinction. They attack and eat livestock and pets, causing economic losses to farmers and ranchers and anguish to pet owners, and they compete with human hunters for game such as elk. Are they merely a pest species?

To answer this question, we need to know something about the scientific discipline of community ecology. In colloquial usage, ecology is another word for environmentalism, but as a scientific discipline, ecology is the broadest concern of biology, the science of life. Whereas other branches of biology are concerned with cells, organs, or individual animals and plants, community ecology studies how different species of plants, animals, and microorganisms interact with each other within a biological community. A community might be a forest, a stretch of desert, a national park, a portion of the seashore, someone’s backyard, and so on.

Most healthy, self-sustaining biological communities have four types of members:

  • Producers. These are either plants or green algae that convert non-living matter into organic substances that they incorporate into their bodies through the process of photosynthesis. They feed everyone else in the community, directly or indirectly.
  • Primary consumers. These organisms, mostly animals, eat the producers. Herbivores, such as cows, sheep, and elk, also plant-eating insects.
  • Predators. These organisms eat other consumers. Carnivores, such as mountain lions, wolves, snakes, and ladybug beetles.
  • Decomposers. Mostly microorganisms and fungi as well as insects that eat dung. They break down the tissues of dead plants and animals and animal excrement and make the chemicals found there available as food for the producers. Nature’s great recyclers.

All four classes of organisms are important to a healthy ecosystem. If one class is diminished, an imbalance occurs which disrupts the nutrient cycle, makes it harder for other species to thrive, and reduces biodiversity. For example, without decomposers like bacteria, dead plant and animal matter can’t be recycled for plants to use, and the nutrient cycle is disrupted. Without plants to make food, primary consumers cannot survive, and soon, neither can the predators that feed on them. Without predators, consumers become too numerous and become destructive of the plant species off which they feed.

National Public Radio’s Morning Edition Show recently broadcast a story on this topic entitled When Big Carnivores Go Down, Even Vegetarians Take The Hit. The broadcast is a little more than three minutes, and you can read it (and listen to it) by clicking here.

A good example of this discussion is the Yellowstone Park community. Wolves were exterminated there as they were in most of America in the 1920’s, but were reintroduced in 1995. First, here is a link to a video on the topic entitled Predators by Bill Ripple, which you can view by clicking here.

Here is an excellent essay on wolves in Yellowstone that appears on the website of the Wyoming chapter of the Sierra Club, which I am reprinting here, in compliance with the Sierra Club’s Terms and Conditions of Use. It was written by members of the Western Wolf Coalition. It explains what the wolf has done for the Yellowstone Park ecological community:

Ecological Benefit of Wolves

Wolves play a vital role in maintaining the health and sustainability of the landscape in the greater Yellowstone region and our western lands. They are a keystone species, one that has a disproportionate impact on its environment relative to its abundance. Since their return in 1995, wolves have benefitted this ecosystem by regulating prey numbers and movements—allowing streambank habitats to recover, reducing densities of coyotes, and providing food for scavengers.

The most recognized and well-documented ecological benefit of wolves is that they have resumed the important role of maintaining healthy wildlife herds in the northern Rockies by selecting young, old, physically impaired, or diseased animals5. By reducing prey numbers, dispersing these animals on the landscape, and removing sick animals, wolves also may reduce the transmission and prevalence of wildlife diseases such as chronic wasting disease and brucellosis7.

In addition to improving the overall fitness of wildlife herds, wolves have also altered the behavior of their prey, leading to a cascade of beneficial effects on the landscape. In the absence of wolves, elk tended to browse heavily in the open flats along rivers and wetlands, since they did not need to evade predators by seeking thicker cover. Without fear of wolves, elk over-browsed the vegetation inhibiting the growth of new trees. Since the reintroduction of wolves in Yellowstone, elk spend more time in the safety of thick cover or on the move6. As a result, riparian areas and aspen groves that had been suppressed by decades of over-browsing are regenerating, improving habitat for species like beavers and songbirds3. Beavers, which create wetland habitats with their dams, have improved water quality in streams by trapping sediment, replenishing groundwater, and cooling water.

Species that rely on healthy riparian habitats and benefit from the presence of wolves in Yellowstone National Park include:

  • Yellowstone cutthroat trout and other native fish
  • Moose
  • Waterfowl (ducks, geese, trumpeter swans)
  • Songbirds (such as warblers, wrens, and thrushes)
  • Small mammals (such as beavers, muskrats,
    and other rodents)
  • Insects, amphibians, and countless other species3,6

Wolves and Coyotes

In the absence of wolves, coyotes became a top predator in the ecosystem, but they are not large enough to regulate elk, deer, and moose populations2. The return of the wolf restored a natural complement of predators to northwest Wyoming and returned the coyote to its role as a mid-level predator. Wolves will kill coyotes and outcompete them at kill sites. Coyotes also prey heavily on pronghorn fawns. Since wolves returned to the landscape, pronghorn populations have increased in northern Yellowstone as a result of declining coyote populations and densities 1.

Wolves and Scavengers

Scavengers, such as ravens, eagles, and bears, also benefit heavily from the return of wolves. Wolf kills provide scavengers with an important source of protein, particularly in winter. Twelve species of scavengers are known to visit wolf kills in Yellowstone National Park 10. Ravens are especially attuned to wolves and may fly over wolf packs as they pursue prey, allowing them quick access to wolf kills. In turn, wolves may benefit from ravens by following them to carcasses that can feed both species8.

Prior to the reintroduction of wolves, scavengers were more dependent on animals that died due to harsh winters. Since snow is thawing earlier as a result of a warming climate, there are fewer winter kills available for scavengers. Wolf kills may help buffer the impacts of climate change for scavengers by providing them with a food source in the winter9.


The return of the wolf to Wyoming has had significant ecological benefits in a relatively short period of time. Ecological concerns contributed to the decision to return wolves and should play a role in how states manage this keystone species. Although it is easy to focus on the perceived negative impacts of wolves, it is important to recognize the actual benefits they provide to our ecosystem. By regulating wildlife herds and reducing the prevalence of diseases, revitalizing riparian areas, reducing coyote densities, providing food for scavengers, and indirectly improving conditions for a host of other species, wolves play an essential role in maintaining the ecological health and integrity of the landscape.

Footnotes to this article

  1. Berger, K.M., E.M. Gese and J. Berger. 2008. Indirect effects and traditional trophic cascades: A test involving wolves, coyotes, and pronghorns. Ecology 89:818-828.
  2. Berger, K.M. and E.M. Gese. 2007 Does interference competition with wolves limit the distribution and abundance of coyotes? Journal of Animal Ecology 76:1075-1085.
  3. Cooke, H.A. and S. Zack. 2008. Influence of beaver dam density on riparian areas and riparian birds in shrub steppe of Wyoming. Western North American Naturalist 68: 350-364.
  4. Halofsky, J.S., W.J. Ripple and R.L. Bestcha. 2008. Recoupling fire and aspen recruitment after wolf reintroduction in Yellowstone National Park, USA. Forest ecology and management 256(5):1004-1008.
  5. Mech L.D., D.W. Smith, K. M. Murphy, and D. R. MacNulty. 2001. Winter severity and wolf predation on a formerly wolf-free elk herd. Journal of Wildlife Management 65:998-10
  6. Ripple, W.J. and R.L. Bestcha. 2006. Linking wolves to willows via risk-sensitive foraging by ungulates in the northern Yellowstone ecosystem. Forest ecology and management 230(1-3):96-106.
  7. Smith, B.L. 2005. Disease and Winter Feeding of Elk and Bison: A Review and Recommendations Pertinent to the Jackson Bison and Elk Management Plan and Environmental Impact Statement.
  8. Stahler, D.R., B. Heinrich and D.W. Smith. 2002. Common ravens, Corvus corax, preferentially associate with grey wolves, Canis lupus, as a foraging strategy in winter. Animal Behaviour 64(2):283.
  9. Wilmers, C.C. and W.M. Getz . 2005. Gray wolves as climate change buffers in Yellowstone. PLoS Biology 3:571.
  10. Wilmers, C.C., D.R. Stahler, R.L. Crabtree, D.W. Smith and W.M. Getz. 2003. Resource dispersion and consumer dominance: scavenging at wolf- and hunter-killed carcasses in Greater Yellowstone, USA. Ecology Letters 6:996–10

© 2013 Sierra Club. All Rights Reserved.

I also came across another excellent article on wolf ecology, this one entitled Wolves As Engineers of Biodiversity, published by the California Wolf Center, which I won’t reprint but you can view by clicking here.

Topic: Should the Wolf Be Removed From the Endangered Species List?

This post begins a new topic: Should the wolf be removed from the list of animals protected by the Endangered Species Act (ESA)? The topic consists of five posts. If you came here via a link, you can navigate between posts by clicking on the arrows that appear above the post heading. The right arrow (→) always points to the next post; the left arrow (←) always points to the previous post. In this particular post, the right arrow is labeled Why Wolves are Important and points to the next post. The left arrow is labeled Gun Homicides vs. Gun Ownership and points to a previous topic.

The last three posts have footnotes which list my sources but also have additional notes and links, so you might want to take a look at them.

If you have a comment, please feel free to type it on the bottom of the post, or send an email to . All constructive criticism is most welcome!

Recently, I received an email from the Natural Resources Defense Council (NRDC):


Dear Michael,

The future of America’s wolves is in jeopardy

The Obama Administration’s new proposal would scrap vital protections for gray wolves across most of the Lower 48 states. Help us send one million messages of opposition to this disastrous plan and give wolves a fighting chance at recovery!

The clock is ticking down for our nation’s wolves.

The Obama Administration has given the public just 90 days to comment on its disastrous plan to strip wolves of their vital Endangered Species Act protections across most of the Lower 48 states.

NRDC and other conservation groups have set an ambitious goal of generating one million messages of protest to stop this far-reaching assault on wolves.

Please do your part by telling the U.S. Fish and Wildlife Service to reverse its reckless plan and give wolves a fighting chance at recovery!

The return of gray wolves to areas like the Northern Rockies and the western Great Lakes has been one of the greatest conservation success stories of our time.

But wolves are only starting to return to large portions of their former range, like the Pacific Northwest. Lone wolves have crossed into California, Utah, Colorado and states in the Northeast.

Removing federal protections now would shut the door on wolf recovery long before the job is done.

This reckless plan, more the result of political pressure than sound science or policy, would throw national wolf recovery into reverse.

In fact, a group of the nation’s top wildlife scientists has sent a letter to the administration, objecting to its proposal.

Wolves will not recover unless they remain protected. That’s why it’s so critical that we keep the pressure on that agency to withdraw this horrendous plan.

Please send your message to the Fish and Wildlife Service right now. Call on them to keep wolves protected under the Endangered Species Act.

We’re at a crucial turning point in this fight — one that will determine whether wolves are allowed to survive and thrive in America. Thank you for making your voice heard in their defense.


Frances Beinecke
Natural Resources Defense Council

I am not criticizing this request. It’s perfectly reasonable, and it asks citizens to speak up on behalf of a cause that they believe in. That is what democracy is all about. Nevertheless, the ad is wanting from a scientific perspective. It makes an assertion which it does not back up with evidence, although the evidence may indeed exist. That assertion is that while the wolf population in the lower 48 states has been allowed to recover, removing Endangered Species Act protections will reverse that recovery. As the email above puts it, “This reckless plan … would throw national wolf recovery into reverse. … Wolves will not recover unless they remain protected. … We’re at a crucial turning point in this fight — one that will determine whether wolves are allowed to survive and thrive in America.”

What is not clear from the email is what the Natural Resources Defense Council is predicting will happen if Endangered Species Act protection are lifted. Is it that wolf recovery will be arrested and wolf populations will be confined to where they exist now, or are they saying that the recovery is liable to being reversed, and that present wolf populations will shrink or disappear altogether? Let’s take a look at the position of wolves in America and estimate what might happen if Endangered Species Act protections are removed. But before we begin, let’s discuss why it is important to have wolves in our ecosystem in the first place, which in turn answers the question: why should we care? That will be the topic of my next post.

Topic: Gun Homicides vs. Gun Ownership

This is a one-post topic examining the relationship between gun ownership and crimes committed with guns in America.  Strictly speaking, this is not a concern of environmental science.  But it is an issue that can be studied with the same sort of methods and analysis used by environmental science to tackle environmental problems, and therefore an appropriate topic for this blog.

Consider the following question: Is there a correlation between high rates of gun ownership and murders committed with firearms in the 50 states? To help answer it, I found three sets of data:

  • FBI 2010 crime statistics from their Unified Crime Reports (UCR).
  • U.S. Census Bureau 2010 statistics on population.
  • Washington Post, quoting a Center for Disease Control (CDC) 2001 survey on gun ownership.

The last source is problematic as it was done in 2001 rather than 2010. I’m assuming that gun ownership percentages did not change significantly between 2001 and 2010, but I could be wrong1. It is also not an exact count but an estimation using samples. There is no official record of who is a gun owner in America. If you recall, the gun lobby is vehemently opposed to a national gun registry, and so we can only estimate the number of gun owners using surveys. This particular survey was conducted in all 50 states by the Centers for Disease Control’s Behavior Risk Factor Surveillance System. Respondents were chosen at random and were asked the following question: Are any firearms now kept in or around your home? Include those kept in a garage, outdoor storage area, car, truck, or other motor vehicle.

Therefore, when the survey states that 41.7% of respondents in Missouri claimed to have a firearm in the household in 2001, it doesn’t necessarily mean that 41.7% of all households in Missouri have firearms. There is a confidence interval or margin of error surrounding the sample statistic within which the true percentage is likely to fall. For example, suppose the 95% confidence level is plus or minus 3%. Then if 41.7% of the Missouri sample answered yes to the question, I can claim with 95% confidence (that is, I expect to be right 19 times out of 20) that the true percentage of Missouri households possessing firearms is somewhere between 38.7% and 44.7%. I still use 41.7% in my calculations because that is my best estimate, but readers must understand that the results of those calculations are going to be fuzzy.

Actually, I tend to think that gun owners are underrepresented in these surveys. I suspect many gun owners are chary about admitting they own a gun, and may refuse to participate or may lie (think about it, if a stranger called you up and asked you if you owned a gun, would you readily admit it?). But unfortunately this survey is the best we can do for now, so we will use it with the understanding that its results may not be totally precise, but with the belief that they are not far from the truth.

I blended the three sets of data into one spreadsheet. Please click here now to view the spreadsheet (a spreadsheet program such as Microsoft Excel™ or OpenOffice Calc is required to view the spreadsheet).

As you can see, the states (and the District of Columbia) are sorted by percentage of households possessing a firearm in ascending order. Some states such as Hawaii have low ownership percentages and low firearm murder rates, but many other states such as Idaho, Montana, South Dakota, and Montana have very high firearms ownership percentages but also have very low firearm murder rates. Louisiana has a high ownership percentage and the highest firearm murder rate in the country, but Maryland, Delaware, and New Jersey have comparatively low ownership percentages but have disproportionately high firearm murder rates.

That suggests that levels of gun ownership alone cannot predict the firearm murder rate and I think there is a great deal of truth to that. However, if we view a scatter plot of the data, the picture proves a little more complicated. I couldn’t get my graph software to draw the plot I wanted, so I drew it myself. Please forgive its crude appearance. When I get the satisfactory software, I’ll redo it. Here is the graph:Murders vs Gun Ownership2

The graph shows states with relatively low firearm ownership levels with both high and low levels of murder by firearm, and states with relatively high firearm ownership levels with both high and low levels of murder by firearm. But there also appears to be some structure. There appears to be an arc of states, going from left to right, Hawaii, Massachusetts, Rhode Island, Connecticut, New York, Illinois, California, Florida, Delaware, Arizona, Pennsylvania, Michigan, South Carolina, and Mississippi. This arc, which is made up mainly of heavily populated eastern states (and California), suggests a mathematical relationship between level of firearm ownership and murders committed per 100,000 people, logarithmic, I think.

Above this logarithmic curve are New Jersey, Maryland, Missouri, and Louisiana. Beneath this curve in the medium-to-heavy firearm level range are three tiers of states.

Right beneath the curve are New Mexico, Georgia, Virginia, North Carolina, Tennessee, Ohio, Texas, Oklahoma, Kentucky, Alabama, Arkansas, and Alaska. Most of these states are southern with considerable economic activity.

Below that in the second tier are Indiana, Kansas, Washington State, Nebraska, Wisconsin, and West Virginia. Mostly midwestern states.

On the bottom tier are Colorado, Maine, Minnesota, Oregon, Utah, North Dakota, South Dakota, Idaho, Montana, Wyoming, Iowa, New Hampshire, and Vermont. Mostly a mixture of midwestern and western states, many of them sparsely populated.

I have an hypothesis why this is so. When I divide numbers of murders committed by population, I’m assuming that all other factors being equal, number of murders committed varies linearly with population. Double the population, and you double the number of murders. But perhaps that is not so. Supposing, all other factors being equal, murders varied with the square of population, that is, if you double the population, the number of murders rises four-fold. That might explain why sparsely populated states have much lower rates of murder by firearm.

There may be other factors as well which should be investigated. Perhaps states with lower-than-expected murder rates:

  • Have lower gang or organized crime activity. The presence of gangs or other forms of organized crime can push up the murder rate significantly.
  • Have a culture of respect for guns and have in place strong social inhibitions regarding the abuse of guns. It is understood that guns as weapons are to be used only in self defense, never to settle an argument.
  • Have less residents who are members of dysfunctional subcultures, such as the subculture of many inner cities, that glorify or at least tolerate violence.

Of course, my analysis is wholly inadequate to base public policy on. States are large, heterogeneous places. I really should take a look at a few states and analyze them county by county. Does the Texas panhandle have the same characteristics as Houston or Dallas? Does central Florida have the same characteristics as Miami or Orlando? Are all the counties in Iowa the same or do they have different murder rates?

Nevertheless, this simple analysis does lead me to some conclusions. First, that restricting gun ownership may not be necessary to address the problem of gun violence. Also, that it may not be fair to demand one Federal gun policy for all 50 states. Why lay restrictions on Wyoming with its low murder rate? Wyoming doesn’t have a gun problem (at least with regards to crime). Neither does New Hampshire or Iowa. New Jersey has a gun problem. So does Maryland, Missouri, and Mississippi. Louisiana and the District of Columbia have a really big gun problems, and that’s where we should be focusing our energies.

One thing we should demand from all 50 states is their cooperation in preventing the purchase of firearms in their states with the intention of committing crimes in other states. But other than that, I would leave low-gun-crime states like Wyoming alone.

Where we need much tougher gun policy is in states and areas that have higher rates of murder by firearm. I would want to first concentrate on those states that form the logarithmic curve that I mentioned above. I would then want to spend special attention on those four states that have even higher rates: New Jersey, Maryland, Missouri, and Louisiana. Less urgent are those states in the first two tiers below the curve.

As I mentioned in a previous post2, to effectively target gun violence we need to target the most important sources of gun violence: gangs, robbery, and especially arguments, the cause of 40% of all gun homicides in the U.S.3 We need to gain the upper hand on gangs, particularly juvenile gangs. We should concentrate on the most likely weapons to be used in crimes: handguns, and not shotguns, rifles, and the so-called assault weapons which are used in the most sensational crimes but are involved in only a small minority of homicides3. By directing our efforts wisely, we should be able to reduce the level of gun violence in this country.


  1. New York Times, “Share of Homes With Guns Shows 4-Decade Decline” by Sabrina Tavernise and Robert Gebeloff, March 9, 2013 (click here to read). The article references two surveys done on gun ownership in the U.S. The first, the General Social Survey (GSS) has been conducted by the National Opinion Research Center (NORC) every year since 1973. It shows a general decline in gun ownership as a percentage of American households (click here to read). The second survey is by the Gallup organization. The New York Times article claims that Gallup found less of a decline in gun ownership, but when I went to the Gallup site, I found that their report claimed that gun ownership is at an all-time high (click here to read). Even according to the GSS, the decline in gun ownership shows little change from 2000 to 2006, (34.3% to 34.5%) so my figures should not be that far off and my conclusions should hold.
  2. “Background Check Bill Goes Down in Defeat”. Click here to read.
  3. United States Census Bureau website, The 2012 Statistical Abstract, Law Enforcement, Courts, & Prisons: Crimes and Crime Rates, specifically “Murder Victims–Circumstances and Weapons Used or Cause of Death”. To view, click here, then go to option 310. You can choose having the data displayed as a PDF file or on an Excel spreadsheet (although OpenOffice Calc works just as well).