Trees, Soil, and Water:

Transcription

1 Trees, Soil, and Water: Green Infrastructure for a Changing Climate presentation to the APWA Symposium on Climate Change Tempe AZ, April David McDonald Seattle Public Utilities david.mcdonald@seattle.gov

2 Climate change causes and effects are complex Source for climate graphics: UNEP,

3 What we know: Climate (& related) challenges, next years Intense storm events = stormwater loading, flooding, wind damage Precipitation variability = snowpack, water supply, multi-year variations (e.g. drought) Energy costs & demands: transport, cooling/heating = changing transportation demands, building requirements Agricultural productivity (due to soil loss, fertilizer costs, weather, climate & political disruptions, etc.) = local/global food disruptions, transport costs

4 Lessons from the carbon cycle soil and vegetation matter! Source: UNEP

5 What to do now, in the face of future climate uncertainty? Build resilient infrastructure: flexible, adaptable Integrate ecosystem services as infrastructure: Green Infrastructure = using natural systems (e.g. soils and vegetation) to supplement built systems for: Waste recycling Stormwater management Water supply (& conservation) Food security Energy conservation

6 Climate solutions: green infrastructure s s role Mitigation (reducing greenhouse gases) Soil building to sequester carbon from atmosphere Local/regional economies to reduce transport fossil fuel use Green building reduce lifecycle energy & fossil fuel use Organic waste to compost/soil (not( landfills or incineration) to reduce methane and CO 2 Adaptation ( climate-proofing our cities) Soil building for stormwater mgmt., etc. Water-conserving landscapes City trees reduce energy, improve air, water, environment Local food security planning

7 Soil Benefits of healthier soil: Stormwater infiltration Water conservation (cut irrigation 50%) Biofiltration of urban air & water pollutants Reduced need for fertilizers, pesticides Healthier, drought & disease-resistant plants UW trials, turf on glacial till soil Compost-amended till soil up to 50% reduction in storm water runoff Compost kickstarts soil biology, repairs damaged soils

8 Building healthy soil Require soil BMPs for all new and re-development: Protect native soils and vegetation where possible Restore disturbed soils, by correcting compaction and amending with compost Recycle landscape wastes back into the soil: Shredding leaves and prunings to mulch Grasscycling (mulch mow lawns) Specify compost & mulch for construction erosion control! Stormwater: combine with other Low Impact Development tools, Blanket Berm Washington DOT specifies compost blankets, for cost-effective erosion control and excellent long-term plant establishment. Wetland

9 Organic waste soil life Yard waste, paper, food waste are too precious to burn or landfill we need to return them to the soil! Burning creates CO 2, pollution, little energy Landfilling creates methane (23-60 times more potent a greenhouse gas than CO 2 - only 50-75% of methane is captured by landfill recovery systems) Compost municipal organic collection: food, yard waste (recycle clean paper; compost food-contaminated paper) Reuse fall leaves, prunings (shredded) as mulch Promote on-farm composting of manures, or closed anaerobic digestion with methane capture/use, and composting/reuse of residuals Biofuels production: never at expense of food or soil health

10 Trees Benefits: F F moderation of temperature (cold or hot) for adjacent buildings and street environments a big savings in cooling and heating costs, material stresses Evapo-transpiration of stormwater up to 50% of precip. No irrigation req. (after establishment) if right species & soil Enhance slope and channel stability, reduce erosion Enhance quality of life, public health, habitat, property values

11 Trees What to plant? Select a diversity of hardy natives or locally adapted to the hotter and dryer end of current local climate (look south) Work with local foresters diversity of species gives more chance of success, more resiliency as climate changes Where to plant? Conifers/denser species to north of buildings winter protection Deciduous to south of buildings winter sun, summer shade Every street needs trees; even more in a hotter world

12 Tree preservation Only save the tree if you can save almost the whole root zone! Fence out vehicles & storage Protect roots with of coarse wood chip ( hog( fuel ) ) or gravel Bore utilities rather than trenching through roots If the soil gets compacted, or grade is changed, the tree is (soon) dead Remove and replant where the root zone can t t be saved!

13 Planting trees it s s the soil! Plant trees that can grow to mature size in available soil to get a 100-year lifespan instead of 15 years Trees need 2 cu. ft. of soil access for each 1 sq. ft. of mature canopy area Soil: max 85-90% compaction, min 2-4% 2 organic matter (= 10-15% 15% compost volume in soil blend) Use native soil where possible. Two strategies for soil volume in urban environments:! Structural soils go to Outreach>Structural Soil! Silva Silva Cell or other structures supporting pavement, while maintaining large areas of uncompacted compost-amended soil underneath

14 Building a city of trees Combine good regulation, public works leadership, and community involvement for a durable, adaptive urban forest.! American Forests urban forestry planning resources Tree People successful community projects, creating urban forests as stormwater infrastructure Seattle Green Factor urban tree, vegetation, & green roof guidelines and

15 Water-conserving landscapes Choose plants that fit the site & local conditions: native or locally cally- adapted, pest & drought resistant Minimize lawn area only where needed, put under light tree shade. Build playfields on deep, healthy, well-drained soil. Build healthy soil with compost and mulch Irrigate just through establishment (2-3 3 years) if a landscape can t t make it on local rainfall, replant one that can Where irrigation is necessary, 220 Water Use use smart controllers: ET or 200 Rainfall 180 soil moisture based " Summer 160 Tree canopy cover cuts landscape 140 irrigation water needs of plants below. 120 Plant like the forest: ground 100 cover, understory,, canopy Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec! Water Use (mil gal/day) Rainfall (inches)

16 Local food security To sequester carbon, support sustainable agriculture & forestry to rebuild Earth s soils Regional farmland preservation (including water supplies) Farmers markets and other tools to promote local marketing Near and in-city market gardening Community gardens strategic use of public land Lean path minimizing waste in food distribution & prep Reuse of otherwise-wasted wasted institutional & commercial food (support collection & redistribution systems) Recycling food waste to compost in backyards, institutions, and city collection systems! American Planning Assoc. guides - Seattle - Portland - google Food Security and Community Food Systems

17 When the going gets hot Natural systems ( green infrastructure ) ) have: Lower energy demands Lower maintenance (working with nature is always easier) Higher resiliency = more dependable Are locally empowering and adaptable over time