What is an Urban Forest?
Young people, change makers, and people looking for connection have long flooded to cities to find opportunity, make community and take up residency. Forests were destroyed to make room for industry, homes for humans, horses at first and cars later.
Before 1900 modern cities boasted the worst health records on earth with the most pollution, open sewers and rampant disease. But at the end of the nineteen’s century a movement for bringing trees and shrubs back into the cities was born in American urban centers. Here in California remnants of the early urban forest can be found adjacent to Victorian homes, with certain species taking the lead.
But what are trees doing in cities? And why does a city need the forest?
Beyond the obvious human needs of clean air, water and shade, trees also provide valuable habitat for local wildlife, protect homes from the sun (reducing energy needs/costs) and sequester (capture and store) tons of atmospheric carbon throughout their existence in the urban environment.
Urban Forestry came about because first, there were urban areas that completely removed all living things (aside from humans) in order to make room for human activities linked to commerce,
The element of carbon is cyclical and that living things (especially plants and soil) can capture carbon and store it in their biomass (living wood, living leaves, dead logs, dead leaves, etc). Compost and organic-matter found in fertile soils is carbon rich, because it’s full of dead stuff – dead stuff which was made out of carbon.
Calculating how much carbon a tree can capture and store (sequester) throughout it’s lifetime has been increasingly estimated by governments, universities and environmental organizations. These estimations are translated into carbon calculations. A large tree (over 60 feet tall) at 30 years can capture more carbon than a smaller-port tree (between 25 and 59 feet tall). And even smaller plants capture less carbon because they contain less wood, less biomass and thus, less carbon.
Although trees capture huge amounts of carbon, perennial grasses which are maintained with ruminant animals (like cows, goats or llamas) actually capture more carbon because of the biological processes of perennial grasses. Whenever grass (leaves) are eaten, perennial grasses slough off an equal amount of biomass below ground (meaning their roots cut off an equal amount of carbon below ground, after getting chomped-on above ground).
This is why the great plains states, like Iowa and Kansas have up to 90 ft of topsoil – because these vast perennial grass dominated plains had ruminant animals like horses, zebras and camels all chomping away at these perennial grasses for millennia.
The trees planted on Sunset Boulevard will likely capture over 500 tons of atmospheric carbon over the next 30 years. Additionally hundreds of yards of mulch will be placed around the newly planted trees to build soil organic matter, increase soil water retention capacity and capture carbon into the living soil.
Cultural Diversity and Biodiversity in the CAN! Gardens
Here with Climate Action Now!, we measure our success in several ways. First and foremost, we measure our success in diversity and participation. Our botanical selections represent our City’s cultural diversity, with plants represented from throughout the world.
Drought tolerant plants are selected to ensure longevity, and adaptation to California’s dry climate.
Flower production throughout the seasons increased forage capacity for local pollinators, creating hubs of biodiversity where pavement once dominated.
Diversity in the urban forest is key as the climate changes. Local trees (California native trees) like Monterrey Cypress, California Buckeye, Coast Live Oak will thrive in the Sunset District’s coastal dunes. Southern California island trees like the Catalina Ironwood and Island Oak. These trees were selected because precipitation patters are more and more resembling southern California every winter.
And exotic trees were selected for this reason as well. It is said that if you want to know what California’s climate will feel like in 20 years, look at Australia today. Australia is a very dry continent, but parts of the country share California’s “Mediterranian climate.” Trees from that part of Australia perform very well in California because the climate is similar – and even boasts more precipitation than our southern hemisphere comrads. Species from New Zealand (New Zealand Christmas Tree), Norfolk Island and Cook Island (Norfolk and Cook Island Pines) perform well in California for similar reasons.