| Another example of this commitment in the Puente Hills to the corridor principle of preserving genetic variability was the 1999 purchase of a former 25 acre avocado plantation in Hacienda Heights, for an undisclosed sum, because it was the best remaining open space wildlife crossing on the west side of Harbor Blvd. Native plant restoration is also being done here to try to return the land to a more natural habitat, and thus more appealing to man and animal alike. There is even a plan to build a wildlife underpass at Harbor Blvd. to make animal migration even safer for them and for motorists (Puente Hills Landfill Native Habitat Preservation Authority, nrm.shtml). Construction just began late this summer, with $1.2 million in federal funding being secured for this project (Puente Hills Landfill Native Habitat Preservation Authority, pdf/Underpass9_05.pdf). These and other similar examples demonstrate that, although somewhat controversial, there is a firm commitment in these hills to the wildlife corridor principle as a means of preserving what remains of our natural heritage and wildlife diversity. It is with this same commitment in mind that Tonner Canyon first comes into focus as a key component of the Corridor, because it shares the same “last link” urgency as Coal Canyon in regards to maintaining connectivity between the habitat areas. The trouble here is the busy 57 Freeway, which bisects the hills and forms a practically impassible barrier to animal movement due to its heavy traffic flow. The Tonner Bridge, where Tonner Canyon Road crosses under the 57, is stated to be “the only functional crossing beneath the 57 for deer, mountain lion, bobcat, and other wildlife species” (Spencer, 2005, 26). Mountain lions are noted in Canada as having a preference for underpasses next to drainage systems, whereas deer tended to avoid them (Clevenger and Waltho, 2000, 53). The Tonner underpass actually has both, with a stream running parallel to the road on the south side, but not visibile form the other side of the road due to a 10 foot drop in elevation from the road to the streambed, making for an almost ideal wildlife passage. It is this underpass that is threatened with a possible new road through Tonner Canyon to relieve congestion in Diamond Bar, which would permanently sever this connection, and this issue will be highlighted in more detail later. 2. The System-Wide Puente/Chino Hills Corridor Idea The benefits to both native species and people of a fully functioning and biologically healthy wildlife Corridor will be discussed, and why it is crucial to provide enough habitat for native plants and animals to have the resources that they require to make long term survival possible. Wildlife corridors only work if they have larger, healthier ecosystems on either side of the passage; therefore it is necessary to preserve larger areas of intact habitat if species are to have a chance to survive. One study found that although many mammals used corridors such as underpasses, ecologically healthy habitat on both sides of the corridor was a major factor in predicting how often it was used (Ng et al, 2004, 499). We now switch our focus from narrow channels of travel between core habitats to the entire collection of ecosystems that make up these hills. So the concept of the Puente/Chino Hills wildlife Corridor is born. Nature conservation needs to be more than just a collection of corridors. The projected biological value of an area needs to be considered, distinguishing “between those sites that can both support resident animals and facilitate the movement of transient individuals from others that provide only a conduit for the movement of wildlife”, emphasizing “the potential of such areas to contribute to metapopulation viability by being large enough to support both resident and transient animals” (Lindenmayer and Vix, 1993, 629). Specific corridors such as the Coal Canyon and Tonner Canyon underpasses provide the conduit for wildlife movement, but the wildlife Corridor (the Puente/Chino Hills) as a whole is large enough to both move and maintain species populations, ensuring metapopulation viability, which means “a set of local populations connected by migrating individuals” (Sharov, 1995). It has been estimated that it takes a habitat area of about 1000-2200 square kilometers of proper habitat to support a mountain lion population, allowing 15-20 cougars to survive. The Corridor, including the Santa Ana Mountains, is about 2070 square kilometers of cougar habitat, so that every piece of land lost to development or cut off from the Corridor greatly increases the risk of local extinction (Beier, 1993, 99,103,104). The general consensus is that it is better not to find out exactly how little land it takes to support a functioning ecosystem, because a miscalculation can result in disaster. |
| Tonner Canyon and its Significance to the Puente/Chino Hills Wildlife Corridor |