Much of my work involves inspection of trees to assess health, stability and structural integrity, and subsequent composition of associated arborist’s reports to document such assessments. These reports are necessary for the issuance of permits to remove mature trees within many municipalities. They are only effective for that purpose if they recommend and justify removal.
If there is nothing wrong with the health, stability or structural integrity of subject trees, removal might be justified for other reasons. For example, the removal of superfluous trees might be justified if it would promote healthier development of remaining trees. Trees that disperse roots that are beginning to damage adjacent infrastructure might likewise need to be removed.
It seems like it is too much to be concerned with for something that property owners should not need permission to remove from their own property. For what people pay for property here, they should be able to do whatever they want to with it. However, mature trees are considered to be assets to their respective Communities, and components of the collective urban forests.
These majorly and justifiably controversial concerns are actually not the the only difficulties associated with municipal tree preservation ordinances.
While a young coast live oak in the extreme corner of my garden was not quite big enough to require a permit for removal, I asked the next door neighbor if he would like it to be removed before the roots damaged his driveway. I explained that if we waited any longer, the tree would be protected, and that a permit to remove such an exemplary tree would not likely be issued.
Tree preservation ordinances are often the motivating factor for the removal of trees before they get big enough to be protected! I was fortunate that my neighbor wanted my oak to stay.
It has been naturalized in Southern California long enough to seem to be native. California pepper, Schinus molle, is actually endemic to Peru and adjacent arid regions of South America as far south as Central Argentina. Furthermore, although its small pink fruits with hard black seeds are sometimes used for culinary purposes, it is actually not related to black pepper, and is mildly toxic.
Recycling plant material is practical and gratifying. We do quite a bit of it here. Back in September, I
Climate is why the European larch, Larix decidua, is so rare here. It prefers cooler weather in both winter and summer, and more humidity. Foliage can roast if too exposed through summer. Small trees that are partly sheltered or partly shaded by larger trees have the best color and foliar density. Larch are innately reliant on somewhat regular watering, so are not drought tolerant. The mildly cool weather of autumn is enough to brown the formerly bluish foliage, which falls shortly afterward.
For a tree that is native to the upper elevations of the Rocky Mountains, blue spruce, Picea pungens, does surprisingly well here. It only wants to be watered a bit through summer to compensate for the lack of rain and humidity in chaparral climates. It does not seem to miss a more pronounced chill through winter. Disease and insect infestation are uncommonly noticeable or damaging.
Spruce happen to very compatible with the landscape style here. They fit in nicely with surrounding redwoods, but are more proportionate to sunny spots of some of the refined landscapes. We intend to add a few into some of the landscapes as they get renovated. They will stay branched to the ground, like big dense shrubbery, with the personality of distinguished forest trees.
One might surmise that a tree that is resilient enough to be the state tree of Texas is not too discriminating. If it can take the heat and humidity of the Lone Star State, it can make it anywhere! However, pecan, Carya illinoinensis, actually prefers heat and humidity, and is bored with the mild local climate. The nuts and the mess that comes with them are actually less abundant than they would be in the Gulf Coast States. The deciduous foliage is not quite so colorful in autumn.
Roots hold up trees. That is part of their job. They grow along with the trees they support, and disperse as necessary to maintain stability. Trees grown within the confinement of cans (pots) or boxes, and then installed into a landscape, are typically staked temporarily until their roots adequately disperse and stabilize. Once unnecessary, 
Even though it can get about fifty feet tall and wide, Italian stone pine, Pinus pinea, often gets planted as a small living Christmas tree into confined urban gardens. It gets so big so fast that it can get to be a serious problem, as well as expensive to remove, before anyone notices. It is really only proportionate to large public spaces such as parks or medians for big boulevards. The bulky trunks typically lean one way or another. The long limbs spread laterally to form an unusually broad and flat-topped canopy.
Christmas trees are like vegetables. Really, they are like big vegetables that do not get eaten. They are grown on farms, and then harvested and sent off to consumers. Although they smell like a forest, and they are descendents of trees that naturally grow in the wild somewhere, there is nothing natural about their cultivation. In fact, most are grown a very long way from where their kind are from. Therefore, bringing a cut Christmas tree into the home takes nothing from the wild, and does not interfere with nature any more than eating vegetables does.