Armillaria root disease, also known as “oak root fungus,” is caused by Armillaria mellea. This fungus is native to forest trees in California. Its range includes the Central Valley, the San Gabriel Valley, the Coastal Mountains, and elevations up to 6,000 ft. of the Sierra Nevada. The pathogen known as Phythophora Root and Crown rot is a type of spore that lives in the soil, and is prevalent throughout the US.
Both of these are devastating gardens all over Southern California, including mine. I've spent the better part of the last two days dealing with identification through soil samples with LA County Agriculture and discussing this with knowledgeable nurseries and gardeners. It's quite a project to deal with these spores and fungi that are attacking the woody plants (azaleas, camellias, some of the roses) because of the humidity that's been so prevalent over the last few years, and the very cool summer we've had this year that keeps moisture in the ground. So the plants are losing the battle, and I'm looking at some ways to balance the humidity with plants that can tolerate them, as well as shifting the soil acidity. This changing humidity and increasing heat are creating the conditions that make it difficult to keep a garden healthy and "breathing". There's also the aspect that gardens are small, isolated fragments of nature and don't work together except as a possible urban tree canopy, which might just point the way towards re-establishing some healthy biospheres in suburban areas.
There's some interesting maps that show how land use change and forest fragmentation upsets the natural balance of the original ecosystems.
Loss of open space is a very real threat to the ability of ecosystems to repair themselves and remain in reasonably good health.A number of recent assessments cite the loss of open space as a top threat to the health and sustainability of ecosystems. This loss also reduces the ability of forests and grasslands to provide a multitude of public benefits, services, and products, including clean water and air, wildlife habitat, scenic beauty, and recreational opportunities.
Loss of open space has three aspects:
1. conversion – the replacement of natural areas with buildings, lawns, and pavement,
2. fragmentation – the division of open space into smaller isolated areas, and
3. parcellation – the subdivision of large acreages into smaller ownership parcels.
These processes must be stopped in the wilderness areas of Southern California because they're so destructive to the ecosystem. This urban fringe needs to pull back, and tracts of wilderness re-introduced so that the system can balance itself over time. Mountainous ridges, valleys, canyons and creeks must be protected and restored, not developed. There are also tremendous possibilities in urban fringe areas and properly managed suburban areas for re-establishing functional ecosystems by changing the kind of development that's allowed there.
It will involve a complete change in the thinking about what constitutes acceptable building practices, as well as a large reduction in paved areas. Which means that the automobile and its resulting sprawl will have to reverse its expansionary course. This produces completely different planning and building models, based upon passive principles and the blending of structure directly into nature and enhancing its processes. This is known as biomimicry, and has started to emerge as a design and planning principle that goes way beyond "green" into a rather radical regenerative strategy.
This is necessarily the way of the future, to live within nature rather than to obliterate it.