matt ritter

Arbor Day Foundation hardiness

zones reflect warmer climate

1990

2006

Climate Change Projections

% of Human Population

Biodiversity is diminishing at a rate even faster than the last mass extinction at the end of the Cretaceous Period, 65 million years ago, with possibly two-thirds of existing terrestrial species likely to become extinct by the end of this century — the vast majority of them unknown to science at the time they disappear - Peter Raven, 2011

Foreword by Peter Raven

What role can we play in helping the problems facing our planet and our future?

1. Work for more species diversity in California’s

urban forests

Origins of California’s Urban Trees

California Native Trees in Municipal Forests

• 9,100 species of plants in California

• ~6,000 native species• 294 tree species• 78 species are suitable for

urban environments• 20 species commonly used

in urban forests

Evolutionary

Relationships

Among California’s

Commonly

Cultivated Trees

Tree Species in the Urban Forest• All phyla and 83% of orders

with trees are represented in California

• Largest genera in California (most species):• Eucalyptus • Quercus • Acacia • Pinus • Acer

Diversity in Urban ForestsJ.C. Raulston’s Second Law

of Landscape Plant Diversity:

In any given region of the United States, 40 shrubs and trees make up 90% of the landscape plantings.

Diversity in Urban Forests

Muller and BornsteinArb. & Urb. For. 2010. 36(1): 18–27

309 species

Diversity in Municipal Forests• 188 – Average # of species on California

municipality tree surveys• 49 – Average # of species on California

municipality approved planting lists• Only 29% of existing species are approved for

future planting• According to Lawrence Lesser 15 species

account for ~50% of planted trees in Southern California

Lesser, L.M. 1996. Journal of Arboriculture 22:180–185.

Promote Diverse Urban Forests• Diverse urban forests are more resilient to

climate change• Diverse urban forests help conserve

biodiversity• Find undeservedly rare trees in your area• Work with cities and nurseries to grow and

plant more species• Experiment with new, appropriate trees• Add 10 new species to your cities approved

planting list

2. Learn your trees and teach

other people about them

“The average person recognizes more than 1,000 corporate logos, but can identify fewer than 10 plants and animals native to his or her locality.” - David Orr

Promote Tree Knowledge• Relearn the trees in your urban forest• Work on making your area’s tree inventory

accurate and up-to-date• Learn species characteristics and plant

appropriate trees• Learn the correct names of trees• Learn the natural history stories of trees• Share those stories with others

3. Promote a clear educational message

about the value of trees

Life without trees is a lower quality life.

Trees Sequester and Store Carbon

Nowak 1994, USDA FS Technical Report, Radnor, PA, pp. 83-94

Trees Reduce Energy Consumption

Carver, Unger, and Parks, 2004, Environmental Management 34: 650-655

Trees Cool Cities

Wilson et. al., 2003, Remote Sensing of Environment 86: 303-321

More Trees = More Wildlife

Donnelly and Marzluff, 2006, Urban Ecosystems 9: 99-117

More Trees Correlate with Lower Crime

Kuo and Sullivan, 2001, Environment and Behavior 33: 343-367 & 543-571

More Trees Correlate with Lower Crime

Kuo and Sullivan, 2001, Environment and Behavior 33: 343-367 & 543-571

More Trees Correlate with Lower Crime

Kuo and Sullivan, 2001, Environment and Behavior 33: 343-367 & 543-571

Trees Promote Happiness

Fuller et. al., 2007, Biology Letters 3: 390-394

Life without trees is a lower quality life.

Summary1. Work for more diversity in

California’s urban forests2. Learn your trees and teach

other people about them3. Promote a clear educational

message about the value of trees

The beautiful trees that grace our neighborhoods did not sprout at random. Tree-lined streets have been woven into a living fabric that shades and soothes our souls. In a real biological sense, trees are our home. That is the deepest meaning of the urban forest. - David Paul Bayles