Transcript Understanding Our Environment

Biomes: Global Patterns of Life
Glaciers shrinking in a warming
world – Chacaltaya Glacier, Bolivia
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TERRESTRIAL BIOMES
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Biomes - Areas sharing similar climate,
topographic and soil conditions, and roughly
comparable communities.
 Temperature and precipitation are among
the most important determinants in biome
distribution.
 Most terrestrial biomes are identified by the
dominant plants of their communities.
 Plants share adaptations, but are different
species in different continents.s
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Surface temperatures over time
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Patterns of sea level, 1993-2000
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Dominant mixes of ecosystems show
global patterns
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Human Disturbance
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For Discussion
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With climate change, the distributions of
many species are expected to change.
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What mechanisms might be examined to test
this?
hint: how is this related to concepts of “niche”?
With climate change, the distributions of
biomes are expected to change.
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How is this different from question 1?
What mechanisms would lead to this?
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Questions
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How does climate influence the form of
dominant ecosystems?
How can we agree on defining dominant
ecosystems?
How do humans directly influence biomes?
 Can areas of biomes “collapse”?
 “Collapse” = irreversible change to simpler
state
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Climate influences dominant growth forms
of natural vegetation
hundreds of species
tens of
species
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Tundra
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Boreal Forest
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Conifer Forests
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Boreal Forest - Northern Conifer Forest
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Taiga - Northernmost edge of boreal forest
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Broad band of mixed coniferous and deciduous
trees between 45° and 60° N latitude.
Species-poor. Harsh climate limits productivity
and resilience.
Temperate Rainforest
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Wettest portion of coniferous forests of Pacific
Northwest.
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Temperate Deciduous Forests
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Grasslands (Steppe)
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Deserts
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Tropical Seasonal Forests
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Tropical Rainforests
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AQUATIC BIOMES
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Saltwater ecosystems cover vastly more total
area and contain much greater volume of
water than all freshwater bodies combined.
Aquatic ecosystems are influenced by light
penetration (depth), salt content and
nutrients.
 For lakes and streams, also influential are
adjacent terrestrial ecosystems.
For coral ecosystems, temperature also is
limiting
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Light Penetration
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How do biomes change through time?
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Temperature and moisture have varied
Biomes 3.5 ky in the past
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North America 9 ky in the past
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present vegetation and –18 ky
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Biomes 28 ky in the past
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If change is “natural” why should we be
concerned about modern climate change?
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What would we mean by “collapse”?
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Can humans contribute to collapse?
What actions and consequences would be
involved?
 alter temperature
 alter water availability
 alter ability of organisms to disperse to
adjust to change
 alter ability of organisms to evolve quickly
Some examples
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HUMAN DISTURBANCE
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By some estimates, humans preempt about
40% of net terrestrial primary productivity.
Temperate broad-leaved deciduous forests
are the most completely human-dominated
biome. Tundra and Arctic Deserts are the
least disturbed.
About half of all original wetlands in the US
have been degraded over the past 250
years.
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