Dry lands, high latitudes, and commodities

Dryland Ecosystems

  • Mixtures of co existing trees and grasses

  • Covers 30% of global land area

  • Precipitation is low: 250-700mm/year

  • Both temperate and tropical forms - subject to range shifts with climate change

  • Annual to decadal fires maintain grass-free proportions

  • Evidence globally that shifting toward higher tree abundance

Deserts

  • Low productivity system

  • <10 inches of rain per year

  • Sparsely populated

  • 35% land area, expected to increase with global warming

  • Warming/drying expected to occur faster than in other regions

  • Already at physiological tolerance limit - can’t make it hotter/dryer without consequences

Mediterranean ecosystems/shrublands

  • Cool, wet winters and hot, dry summers

  • Highly susceptible to climate change, vulnerable to contraction

  • Threats; drought, altered precipitation, rising temps, increasing fire frequency

  • Observed changes in phenology, decreased productivity, increased erosion and desertification

Boreal Forests

  • High northern latitudes, cold, wet, boggy with short growing season

  • Large Carbon reserves in organic soils and permafrost

  • Warming is causing boreal forests to move into tundra zone, drought in southern range limit causes browning and forest dieback

  • Melting permafrost leads to large CO2 and CH4 fluxes

  • Change is more predominant in North America due to tree species

Tundra, Permafrost

  • Warmed much faster than global average

  • Warming is causing permafrost thawing and increase in soil “active layer”

  • Frozen soils contain large amounts of Carbon

  • Woody shrub encroachment and increased NPP in all vegetation types - changes micro-climate and biophysical feedbacks, increasing the rate of change

  • sea-ice retreat further enhances terrestrial NPP and stresses arctic animal populations

  • It is virtually certain that rapid change will continue even with stabilization of GHG emissions

  • Positive feedback loops force an ecosystem into a different steady state

  • Negative feedback loops maintain a system in a steady state - homeostasis

Alpine Systems

  • High sensitivity to climate change

  • All high-elevation ecosystems show declining snow cover/glaciers, rising temps, longer growing seasons

  • Vertical migration of ecosystems occurring

  • Forest mortality and enhanced fire regimes

  • Snow adapted organisms (snowshoe hare) show changed in phenology

  • Permafrost thawing

  • Shorter winters threaten winter sport based economies

Commodity Production

Plantation forestry

  • Improvements of silvicultural practices have resulted in productivity gains over last 50 years - very efficient

  • Future potential gains in other parts of the world have potential to increase productivity and help mitigate climate change through Carbon sequestration

  • Developing trees that can tolerate higher temperatures lower water supply and increase biotic stresses (insect pests)

Bioenergy

  • Biomass can be burned directly, co-fired with coal, or converted to liquid transportation fuels

  • “Recycles” atmospheric Carbon

  • Must use low input culture methods (little-no irrigation or fertilization) to keep Carbon footprint small