Destroying Wildlife Habitats

Glen Canyon is home to a lot of birds, animals and other wildlife. There’s the famous Great Horned Owl’s regular nesting tree. Bewick’s wrens nest in Glen Canyon, too, and birders have seen over 50 species there. Then there are animals: coyotes, skunks, raccoons, squirrels, and rodents that are prey for the coyotes and hawks and owls. There are two natural bee hives in tree hollows.


This plan would destroy important habitat for the wildlife that lives here.

Much of the wildlife in the canyon uses or benefits from the tall, majestic trees. The eucalyptus hosts many species and sizes of birds, from the Great Horned Owls to the tiny Brown Creeper. The Monterey pine is habitat for kinds of birds and insects and other wildlife that need conifers.

Even the dead and dying trees that would be cut down have important habitat value: they are critical for cavity nesting birds and animals; they attract insects that are food for woodpeckers and other birds; they host interesting fungi that cannot grow elsewhere. They increase the biodiversity of the environment.

The nativists argue that native plants are better habitat for insects and thus for the whole ecosystem. It’s not true. Recent research from Professor Douglas Tallamy indicates that insects eat non-native plants as enthusiastically as native ones. (Click HERE for an article about that research.)

[Click HERE for a beautiful series of pictures of the Birds of Glen Canyon Park.]


Quite sadly, one pine tree targets for cutting is home to one of the bee hives in Glen Canyon. (This would be in addition to one inadvertently destroyed last year.)  [Edited to Add: Work by the bee-keeping community of San Francisco has apparently resolved this through discussions with the SF RPD. The tree, which is assesses as hazardous, will be amputated at the 60-70 foot level, thus reducing the risk while hopefully preserving the hive.]

Even the lovely, gnarly acacia that provide a screen beneath the towering Eucalyptus along the Rec Center will be gone. Acacia is also an extremely valuable habitat tree; its seeds are a food source for insects and birds, and the thick understory is a place for birds to hide from predators and build nests.



4 Responses to Destroying Wildlife Habitats

  1. Viola Toniolo says:

    Trees are habitat, but eucalyptus trees make very poor habitat, especially for birds and for most native plant species. Eucalyptus removal is good for rebuilding strong, native ecosystems.

    Webmaster: Many people think that eucalyptus is poor habitat (including some of us, before we started to observe and research), but it isn’t true. Eucalyptus especially important because of it’s large, and it’s winter-flowering. It’s not just the Great Horned Owls and hawks that use it, small birds like the brown creeper, kinglets, hummingbirds, orioles all use eucalyptus. The leaf litter is valuable to reptiles of all kinds. Bees depend on it for winter forage. There are a bunch of articles on SaveSutro, a website dedicated to saving the eucalyptus forest on Mt Sutro. And here’s a link to a list of over 40 species of birds found there. Native ecosystems in San Francisco support far fewer species. If you follow the bird-watching lists, most are from areas of non-native trees like Mount Davidson and Golden Gate Park. Only a few sightings are at places like Twin Peaks where a native habitat is being established. Also: Native grasslands require regular pesticide use to maintain. That’s not good for habitat, especially in Glen Canyon which is a watershed.

  2. Viola Toniolo says:

    As an ecologist and ornithologist who worked on riparian and bird habitat restoration projects for years, and I can assure you that while it may seem like birds are using eucalyptus groves, few of them can actually nest successfully in and around eucalyptus. I once spent the better part of a summer searching for songbird nests along Redwood Creek, in Marin County, and the one eucalyptus grove along the creek was the one area with the least plant and bird diversity and the least number of nests. Birds were flying through and using the grove in good numbers because it provided some cover, but they not necessarily finding lots of food or nesting in it. Healthy riparian habitat is one that is biologically and structurally diverse (big trees, small trees, dead trees, grasses, annuals, and shrubs), and eucalyptus do not provide any structural or biological diversity. Glen Canyon has so much potential to support healthy bird, insect, and other small animal populations, but it’s highly degraded and has a lot of room for improvement.

    Hummingbirds do use eucalyptus but their nostrils can get clogged up from consuming the nectar. Orioles are mostly migratory and generally don’t nest in San Francisco – they can just as easily move through if the trees were different, smaller, and more shrub-like. Brown creepers and kinglets are very versatile and not going to have any trouble adapting to the absence of eucalyptus. Hawks and owls are predators, so having too many large trees can be harmful to other, smaller prey species (songbirds, amphibians and reptiles) because the hawks and owls tend to be more abundant in such areas. All of the animals that thrive in the leaf litter will do just as well, if not better, on native plant leaf litter. My honeybees at home have no trouble finding winter forage, and there are no eucalyptus near my house. Bees can travel up to 3 km from their hive. Native bees, which are declining, do not do well on eucalyptus.

    Golden gate park has a lot of bird species because it has a lot of structural diversity. Twin peaks has few species because it has very little structural diversity – it’s a coastal scrub environment. And Mt. Sutro provides good cover for migrants because it’s a stand of large trees on a mountaintop – that is why birdwatchers flock there during spring and fall migration to see species passing through. I can only imagine how many more birds would be able to use Mt. Sutro if the eucalyptus were removed and replaced with lots of trees of different sizes and types – native or not.

    I don’t think the park is trying to establish a native grassland in Glen Canyon. That would make little ecological sense, since the canyon has never been a grassland. I’m guessing that any herbicide application would be highly localized and would serve to target invasive tree species. Such applications are generally done on a short-term basis and have a negligible environmental impact.

    PRBO’s Riparian Bird Conservation Plan is an excellent reference if anyone is interested in learning more about what good riparian habitat should look like, both for birds and otherwise:


  3. Scott R. says:

    I am not certain if this is the correct place to add my two cents to the discussion, but I hope this email reaches the right network of readers who share concern over what is happening in Glen Canyon. I am a long time resident of Diamond Heights (23 years) and owner of a home that borders the park. I feel very fortunate to live in such a beautiful urban forest and I am shocked at how rapidly it is being decimated. I was aware that changes were taking place in the area near the recreation center, but had no idea that deforestation was in the works on the trails behind my home and the impact it would have on wildlife. For the past 5 years I have had the pleasure of listening to the evening howls and chants of the coyotes, and frequent glimpses of them on my daily walks in the canyon, but I have come to realize that they are probably gone forever. The area along the trail (directly behind Turquoise Way) that the breeding pair used as a den to house their pups was completely destroyed last week and since then, no sightings, no more evening chants. This is more than just a personal sentimental concern. Those wild, but shy dogs did a great service to the park by containing the numbers of raccoons, skunks, gophers and rats that invaded homes, gardens and garbage cans. Now instead of a beautiful hammock of trees and a pair of coyotes with pups, we have a barren area that is drying up, where teens skip school to smoke cigarettes (HUGE fire danger!), and people are riding mountain bikes causing irreparable damage to the trails (are bikes legal on the park trails?). My congratulations to the park planners on their great “improvements”. What’s next? A bungee jumping pad from the cliff rocks?
    Scott R.

  4. Jamie says:

    This is absolutely sickening. In the last decade, the fragmentation and destruction of wildlife habitat in the US has become an epidemic. I have enjoyed bicycles and shoes of all kinds, my whole life. But I have never expected wilderness areas or even small scenic vistas to give way to parking lots, sidewalks, educational signs or even gravel trails so that I can learn about nature and experience the romance and wonderment of a pristine environment while running a marathon or competing for the pole position on a mountain bike.

    I grew up loving and learning about nature on my hands, knees, and feet. The arguments used to perpetuate environmental sterilization always revolve around a flaccid veil of education. These places are changing ecosystems forever so that we can ride bicycles and get exercise in places that are more enjoyable to use than the quarter mile track at the 50million dollar stadium and related practice track and stadium that were built for that purpose. The worst abuse comes near waterways. Tracks and roads are being built along streams, lakes, and wetlands everywhere. They are located where amphibious species by definition, live. When the road for hiking is built, something has to be displaced and replaced with gravel, concrete, or asphalt. Why? So that the public can walk or ride through there with comfort. Then of course, there has to be trash cans, restrooms, and the area will need weekly mowing and maintenance. As a result, there is a complete extermination of amphibious wildlife that was once a part of the ecosystem. Species which will survive and flourish will be invasive, and usually related to rats. The only predators they will have will be feral cats and dogs. If there is enough trash and waste, the rodents and predators will live off of that.

    For anyone who enjoys fishing, you will have to find somewhere else to go. The public will vote you out every time. Individual rights are no longer a factor. People will ignore the minority of others who appreciate nature in a true sense, when it comes to a vote because they are being told by the developers and politicians that this will help educate people and promote stewardship. This means that to learn about the environment, you have to change it and spend money. God apparently didn’t do it right. He needs our help. And you need lawnmowers. Something that God didn’t have available when He built the world.

    This has happened so fast that there is not much pristine wilderness left. You people with kids are gonna rip the souls out of your children and experience a never ending disappointment of why they have no longing for adventure or romance, or intrigue into matters of biology or science, unless it has something to do with weaponry and warfare. For kids to like something, or love something, it has to have a factor of difficulty to enjoy. At least to get their feet dirty. Most of us were kids once. I was one too. I was one who was fascinated with wildlife. I was entranced by vastness. I found these things in music and poetry. I saw it in paintings and photography. It translated to love and passion in relationships with people. To me it meant a lot to have somewhere that I could go to be alone. You might find that your less alone in nature than you are in a crowd of people fighting over the last seat on the bus.

    Don’t let your kids miss opportunities to experience life in a stream up to their ankles in clear water, with frogs and bugs and birds and critters. Don’t replace them with toxic rivers and poison. Don’t replace an ecosystem with signs. Don’t tell your kids lies to save them. Tell them that if you’re going to cut down all non-native species of trees, that it is because you didn’t like them nor did you like their associated cohabitants. And besides, they clogged up the hummingbirds noses. Tell them that you don’t really give a f… because unimproved nature doesn’t stimulate the economy. A trail without mowing and maintenance doesn’t produce jobs. Then tell them that you hope someday they may be the privileged professional who gets to mow the trail areas!

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