Plant invasions and climate change – implications for the nursery industry

Topic outline

1. How is climate changing?

2. Rising temperatures and plant range shifts

3. Plant response to rising CO2

Rising CO2 – is this change normal?

Atmospheric CO2

• Risen from 280 pre-industrial

• Near 400 today

• Tied to plant sources (fossil fuels & deforestation)

1. How is climate changing?

What do carbon additions mean for climate?

1. Rising temperatures (stronger greenhouse effect)

2. Altered precipitation (varies by region)

1. How is climate changing?

A bigger concern: More frequent extremes

Southwest: heat waves cause fires Last week

Tem

pera

ture

var

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lity Heat Waves Heat Waves

1. How is climate changing?

A bigger concern: More frequent extremesPr

ecip

itatio

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tens

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Droughts & Floods Droughts & Floods

1. How is climate changing?

A bigger concern: More frequent extremesPr

ecip

itatio

n in

tens

ity

Droughts & Floods Droughts & Floods

Red River flood near Fargo, ND

1. How is climate changing?

Implications of extremes on ecosystems? Increased disturbance = Increased invasion

1. How is climate changing?

% of studies

Top landscape correlates of invasion: Disturbance

Vila & Ibanez, 2011

Take home points:

• Atmospheric CO2 is rising

• As a result, temperatures are also rising. But, a greater concern is more frequent extremes: heat, drought, floods

1. How is climate changing?

Plant communities are shifting poleward and upward

2. Rising temps & range shifts

Range Shifts in Yosemite2. Rising temps & range shifts

Biologist Joseph Grinnell, circa 1922

1914-1920: Grinnell collected over 4000 specimens and 3,000 pages of notes on locations collected

2005: Berkeley & USGS scientists resurveyed the same locations

About half of species ranges showed a significant shift

Species that expanded in range tended to expand upwards

Species that contracted in range tended to do so at lower elevations

American Pika’s range has retreated

How much are native communities shifting?

2. Rising temps & range shifts

~ 1500 ft (in 90 yrs)

~ 600 ft (in 40 yrs)

Native species and ecosystems don’t disperse very fast across landscapes

There is a lot of concern that native species won’t be able to ‘keep up’ with warming

BUT, Ornamental plants get a head start

2. Rising temps & range shifts

Native range of Rock soapwort (Saponaria ocymoides) in Europe

Nurseries selling that plant in Europe

People are way better dispersers of plants than plants are alone

2. Rising temps & range shifts

VS. WIN!

Assisted migration through gardens

2. Rising temps & range shifts

Our choices of garden species will affect native ecosystems in the future

One example - Torreya Guardians support planting of the endangered Torreya taxifolia north of its native range in Florida. New plantsings now established in N. Carolina Torreya taxifolia seedling

Assisted migration through gardens: Also expands invasive species

2. Rising temps & range shifts

Live plant imports are the primary pathway for forest insect and pathogen invasions in the U.S.

An estimated 12% of international imports are contaminated by non-native insects

Contaminated shipments (2003-2010)

Citrus longhorned beetle exit hole in a Maple shipment

Bad News: Projected Kudzu Invasion2. Rising temps & range shifts

2. Rising temps & range shifts

Take home point:

• The ornamental plant trade is the primary facilitator of plant dispersal – for both native and invasive species

Average increased growthTrees: +50%Shrubs: +20%Flowering herbs: +15%

Change to average plant18% more flowers19% more fruits25% greater seed mass

3. Plant response to rising CO2

Plants do better with higher CO2

Invasive plants win with rising CO2

3. Plant response to rising CO2

CO2 fertilization benefits invasives over natives in comparative studies

• CO2 fertilization benefits invasives over natives in comparative studies

• Also, bigger = harder to killAmbient CO2 Future CO2

Canada thistle

3. Plant response to rising CO2

Invasive plants win with rising CO2

Another winner from rising CO2

3. Plant response to rising CO2

Higher CO2 conditions make poison ivy grow faster and become more allergenic

Take home point:

• All plants do better with higher CO2, but relative improvements matter. Watch out for hardier invasives.

3. Plant response to rising CO2

Conclusions• Increased climate extremes and rising CO2

preferentially benefit invasive plants

• Ecosystems are shifting poleward and upward in response to climate change

• Our choices in garden species affect surrounding ecosystems. If possible, plant local(ish)