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Slide 01
Climate Zones & Biomes
- Earth's Living Mosaic
- How latitude, altitude, ocean currents, and atmospheric circulation create the astonishing diversity of ecosystems that blanket our planet.
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Slide 02
Contents
- 01 What Determines Climate?
- 02 The Koppen Classification
- 03 Tropical Climates (A)
- 04 Tropical Biomes
- 05 Dry Climates (B)
- 06 Desert & Steppe Biomes
- 07 Temperate Climates (C)
- 08 Temperate Biomes
- 09 Continental Climates (D)
- 10 Continental Biomes
- 11 Polar Climates (E)
- 12 Polar & Alpine Biomes
- 13 Ocean Currents & Climate
- 14 Altitude & Microclimates
- 15 Biome Biodiversity
- 16 Soils & Biomes
- 17 Climate Change Impacts
- 18 Shifting Zones
- 19 Biome Conservation
- 20 Key Numbers
- 21 Climate Extremes
- 22 Further Reading
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Slide 03
What Determines Climate?
- Climate is the long-term average of weather patterns in a region, typically measured over 30-year periods. Several interconnected factors determine a location's climate.
- Latitude
- The single most important factor. The angle of incoming solar radiation decreases from equator to poles. The tropics (23.5 N-S) receive nearly vertical sunlight year-round, delivering ~2.5x the energy per unit area as polar regions. This energy gradient drives global atmospheric circulation: the Hadley, Ferrel, and Polar cells create predictable wind and precipitation patterns.
- Ocean Currents
- Oceans redistribute ~25% of the sun's energy received at the equator toward the poles. The Gulf Stream warms Western Europe 5-10 C above its latitudinal average (London at 51 N is mild; Labrador at the same latitude is subarctic). Cold currents (Humboldt, Benguela, California) cool western continental coasts and create coastal deserts by suppressing convection.
- Continentality
- Distance from the ocean profoundly affects temperature range. Water has 4x the heat capacity of land, moderating coastal temperatures. Verkhoyansk (Siberia, 67 N) experiences a 105 C annual temperature range (-68 C to +37 C) -- the world's most extreme continental climate. Coastal Bergen, Norway (60 N), varies only 15 C.
- Altitude
- Temperature drops approximately 6.5 C per 1,000 m of elevation (the environmental lapse rate). Quito, Ecuador (2,850 m, 0.2 S) has a perpetual spring climate despite being on the equator. Mount Kilimanjaro (3 S) supports tropical forest at its base and glacial ice at its 5,895 m summit -- encapsulating all major biome types on a single mountain.
- Topography
- Mountain ranges create rain shadows: moist air rises on the windward side, cools, and precipitates; dry air descends the leeward side. The Himalayas block Indian Ocean moisture, creating the Tibetan Plateau's cold desert. The Andes create the Atacama Desert, the driest place on Earth (some stations have never recorded rain). Aspect matters: south-facing slopes in the Northern Hemisphere receive more solar radiation.
- Atmospheric Circulation
- The Intertropical Convergence Zone (ITCZ), where trade winds meet, drives tropical rainfall and migrates seasonally. Subtropical high-pressure belts (~30 N/S) create the world's great deserts. Jet streams at ~10 km altitude steer mid-latitude weather systems. El Nino/La Nina cycles shift rainfall patterns across half the globe.
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Slide 04
The Koppen Climate Classification
- Developed by Russian-German climatologist Wladimir Koppen in 1884, refined by Rudolf Geiger (1954, 1961), this system remains the most widely used climate classification. It uses temperature and precipitation thresholds to define 5 main groups and 30 subtypes.
- Tropical
- Coldest month >18 C. High rainfall. No winter. ~20% of Earth's land.
- Dry (Arid)
- Evaporation exceeds precipitation. Deserts & steppes. ~26% of land.
- Temperate
- Coldest month -3 to 18 C, warmest >10 C. Mild winters. ~16% of land.
- Continental
- Coldest month <-3 C, warmest >10 C. Severe winters. ~21% of land.
- Polar
- Warmest month <10 C. Permanent ice or tundra. ~17% of land.
- Reading the Codes
- The second letter indicates precipitation pattern: f = no dry season, w = dry winter, s = dry summer, m = monsoon. The third letter refines temperature: a = hot summer (>22 C), b = warm summer, c = cool summer, d = very cold winter. Example: Cfb = oceanic temperate (London, Paris) -- no dry season, warm summer. Dfc = subarctic (Moscow) -- continental, no dry season, cool summer.
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Slide 05
Tropical Climates (A)
- Af - Tropical Rainforest
- Am - Tropical Monsoon
- Aw - Tropical Savanna
- Af: Tropical Rainforest
- Rainfall every month (>60 mm), no dry season, mean temperature 25-28 C year-round. Annual rainfall typically 2,000-4,000 mm. Diurnal temperature range (~8 C) exceeds annual range (~2 C). The most thermally stable climate on Earth.
- Locations: Amazon Basin, Congo Basin, insular Southeast Asia (Borneo, Sumatra), western Colombia.
- Key stat: Manaus (Brazil) receives 2,307 mm of rain annually across 200+ rain days. Temperature varies only from 26-28 C month to month.
- Am: Tropical Monsoon
- Pronounced wet season driven by seasonal wind reversal (monsoon). Brief dry season offset by heavy monsoon rainfall. Annual precipitation often exceeds 2,500 mm, concentrated in 6-8 months.
- Locations: Coastal India (Mumbai: 2,167 mm, 95% in June-September), Southeast Asia, West Africa, northern Australia.
- Key stat: Cherrapunji, India, received 26,461 mm in one year (1860-1861) -- the wettest year on record. Mawsynram, 15 km away, averages 11,872 mm/year.
- Aw: Tropical Savanna
- Distinct wet and dry seasons. Driest month receives <60 mm. The ITCZ brings summer rains; subtropical high pressure creates winter drought. Temperature remains warm throughout.
- Locations: Sub-Saharan Africa (the Sahel), Brazilian Cerrado, northern Australia, parts of India, Central America.
- Key stat: The Cerrado covers 2 million km2 (21% of Brazil), making it the world's most biodiverse savanna. It has lost ~50% of its native vegetation, primarily to soybean farming and cattle ranching.
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Slide 06
Tropical Biomes
- Tropical Rainforest
- The most biodiverse terrestrial biome. A 10 km2 patch may contain more tree species than all of North America. Stratified in four layers: emergent (50-80 m), canopy (25-45 m), understory, and forest floor (receives <2% of sunlight).
- Biodiversity: Tropical forests cover 6-7% of Earth's land surface but harbor ~50% of all species. The Amazon alone contains ~390 billion individual trees of ~16,000 species. A single hectare in Ecuador's Yasuni National Park holds 655 tree species -- more than all of the US and Canada combined.
- Carbon storage: Tropical forests store ~250 Gt of carbon in biomass and soil -- equivalent to ~30 years of global CO2 emissions. Deforestation releases ~4.8 Gt CO2/year (2015-2019), making it the third-largest source of emissions after fossil fuels and industry.
- Tropical Savanna & Grassland
- Grass-dominated with scattered trees (typically fire-adapted species like acacias and baobabs). Maintained by the interaction of fire, drought, and herbivory -- without these disturbances, many savannas would become forest.
- Africa's savannas cover ~13 million km2 and support the world's greatest large-mammal assemblages. The Serengeti migration -- 1.5 million wildebeest, 200,000 zebra -- is the largest mammal migration on Earth.
- Fire ecology: Many savanna grasses regrow from root systems after fire. Aboriginal Australians have used fire to manage savanna landscapes for 65,000+ years -- the longest continuous land management practice known. In Australia, these "cultural burns" reduce wildfire severity and promote biodiversity.
- Threat: Savannas are disproportionately threatened by agricultural conversion. Brazil's Cerrado loses 6,000-10,000 km2 per year, faster than the Amazon.
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Slide 07
Dry Climates (B)
- BWh - Hot Desert
- BWk - Cold Desert
- BSh - Hot Steppe
- BSk - Cold Steppe
- BW: Desert (Arid)
- Precipitation less than half the evaporation threshold. Hot deserts (BWh) have mean annual temperatures >18 C; cold deserts (BWk) have mean annual temperatures <18 C.
- Hot deserts form primarily in subtropical high-pressure zones (~30 N/S): Sahara (9.2 million km2, nearly the size of the US), Arabian, Thar, Sonoran, Namib, Australian interior. Diurnal temperature swings can reach 40 C. The Sahara's Aziziya (Libya) recorded 58 C -- though this was later invalidated; Death Valley (56.7 C, 1913) is the accepted record.
- Cold deserts form in continental interiors or rain shadows: Gobi (Mongolia/China), Patagonian Desert, Great Basin (US), Iranian Plateau. The Antarctic ice sheet is technically the world's largest desert by precipitation (~50 mm/year on the plateau).
- BS: Steppe (Semi-Arid)
- Transitional between desert and humid climates. Precipitation is 250-500 mm/year -- enough for grassland but not forest. The world's great grasslands occupy this zone.
- Hot steppe (BSh): Sahel region (southern Sahara margin), parts of Australia, northwestern India. The Sahel (Arabic for "shore") stretches 5,400 km across Africa, from Senegal to Sudan. It supports ~135 million people who depend on rainfall agriculture. Drought-famine cycles are intensifying with climate change.
- Cold steppe (BSk): Central Asian steppe (Kazakhstan, Mongolia), US Great Plains, Argentine Pampas, South African veld. The Eurasian Steppe stretches 8,000 km from Hungary to Manchuria -- the largest grassland on Earth, historically home to pastoral nomads including the Mongol Empire.
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Slide 08
Desert & Steppe Biomes
- Desert Adaptations
- Life in deserts reveals extraordinary evolutionary strategies for heat and water scarcity.
- Plants: Cacti store water in succulent stems; saguaros hold up to 760 liters. Creosote bushes produce allelopathic chemicals that inhibit competing plants, creating evenly spaced "clone rings" -- one in the Mojave is estimated at 11,700 years old (King Clone).
- Animals: The kangaroo rat (Dipodomys) never drinks water, obtaining all moisture from metabolizing dry seeds. Fennec foxes use oversized ears for heat radiation. Namib desert beetles collect fog on hydrophilic-hydrophobic wing surfaces.
- Nocturnal behavior: ~90% of desert animals are active primarily at night. Many burrow to escape daytime temperatures that can exceed 70 C at the soil surface.
- Desert Phenomena
- Desertification: Degradation of dryland ecosystems due to overgrazing, deforestation, and climate change. Affects ~40% of the world's land surface, threatening 2 billion people (UNCCD). The Sahara has expanded 10% since 1920. The Great Green Wall initiative aims to restore 100 million hectares across the Sahel by 2030.
- Desert blooms: After rare rains, desert wildflowers create spectacular displays. Chile's Atacama "desierto florido" occurs every 5-7 years when El Nino brings unusual rainfall. Dormant seeds can survive decades in the soil seed bank.
- Oases: Crucial human habitats in deserts, formed where aquifers reach the surface. Siwa Oasis (Egypt) has been continuously inhabited for 12,000+ years. The Sahara contains ~2 million oases supporting 10+ million people.
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Slide 09
Temperate Climates (C)
- Cfa - Humid Subtropical
- Cfb - Oceanic
- Csa - Mediterranean
- Cwa - Subtropical Monsoon
- Cfa/Cwa: Humid Subtropical
- Hot, humid summers (warmest month >22 C) and mild winters. Found on eastern sides of continents between 25-40 degrees latitude, where warm ocean currents and onshore winds bring moisture.
- Locations: Southeastern US (Atlanta, Houston, New Orleans), eastern China (Shanghai, Wuhan), southeastern Brazil (Sao Paulo), eastern Australia (Sydney, Brisbane), northern Argentina (Buenos Aires), Japan (Tokyo).
- Key fact: The Cfa zone is remarkably productive agriculturally -- it includes the US Cotton Belt, China's rice paddies, Brazilian coffee lands, and Argentina's Pampas grain belt. Dense populations in eastern China and the US South reflect this fertility.
- Cfb: Oceanic & Csa: Mediterranean
- Oceanic (Cfb): Mild year-round, narrow temperature range. Cool summers (<22 C), mild winters (>0 C), rain distributed evenly. Western Europe (London, Paris, Amsterdam, Dublin), New Zealand, Pacific Northwest coastal areas, southern Chile.
- Mediterranean (Csa/Csb): Hot, dry summers and mild, wet winters -- the only climate type with summer drought. Created by seasonal shifts of subtropical high pressure. Found on western continental margins at 30-45 degrees latitude: Mediterranean Basin, California, central Chile, southwestern Australia, South Africa's Western Cape.
- Key fact: Mediterranean climate covers just 2% of Earth's land but harbors 20% of the world's plant species. Five Mediterranean-climate biodiversity hotspots exist, including the Cape Floristic Region (9,000 plant species in an area the size of Maine).
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Slide 10
Temperate Biomes
- Temperate Deciduous Forest
- Broad-leaved trees (oak, maple, beech, hickory) shed leaves in autumn, adapting to seasonal cold and reduced daylight. Four distinct seasons. Found in eastern North America, western/central Europe, eastern Asia (Japan, Korea, China).
- Biodiversity: Rich understory flora capitalizes on spring light before canopy leaf-out ("spring ephemerals"). Eastern US forests contain ~1,100 tree species (vs. ~40 in equivalent European forests) -- a legacy of Ice Age geography. European trees migrated into the Mediterranean and were blocked by east-west mountain ranges; North American trees retreated south unimpeded.
- Temperate Rainforest
- Cool, wet forests receiving 1,500-3,500 mm rainfall annually. Lush mosses, ferns, and epiphytes drape enormous conifers or broadleaf trees. Among Earth's most productive ecosystems by biomass.
- Pacific Northwest: Sitka spruce, western red cedar, Douglas fir forests store more carbon per hectare than any tropical forest -- up to 1,000 tonnes C/ha. Old-growth trees reach 60-90 m and live 500-1,000+ years.
- Other locations: Valdivian rainforest (southern Chile), Tasmania, New Zealand's west coast, Colchic forests (Georgia), British/Irish oceanic oak woods.
- Mediterranean Shrubland
- Called chaparral (California), maquis (Mediterranean), fynbos (South Africa), mallee (Australia), matorral (Chile). Characterized by hard-leaved (sclerophyll) evergreen shrubs adapted to summer drought and fire.
- Fire ecology: Many species require fire to germinate (serotinous cones, smoke-stimulated seeds). California chaparral burns in cycles of 30-150 years; suppression leads to fuel buildup and catastrophic wildfires. The 2018 Camp Fire (Paradise, CA) killed 85 people.
- South Africa's fynbos: 9,000+ plant species, 70% found nowhere else. Proteas, ericas, and restios dominate. More plant species per unit area than tropical rainforest.
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Slide 11
Continental Climates (D)
- Dfa/Dwa - Hot Summer Continental
- Dfb/Dwb - Warm Summer Continental
- Dfc/Dwc - Subarctic
- Dfd/Dwd - Extreme Subarctic
- Hot & Warm Summer Continental
- Large annual temperature ranges (30-60 C between coldest and warmest months). Found exclusively in the Northern Hemisphere -- the Southern Hemisphere lacks sufficient land mass at relevant latitudes. Warm summers allow agriculture; cold winters bring snow and frozen ground.
- Dfa (Hot summer): Chicago (-5 C January, 24 C July), Seoul (-3 C to 25 C), Beijing (-4 C to 27 C). The US Midwest and Corn Belt are Dfa -- producing 40% of the world's corn and soybeans.
- Dfb (Warm summer): Moscow (-8 C to 19 C), Stockholm, Helsinki, Winnipeg. Northern Europe's population center. Growing seasons of 4-6 months limit agriculture to hardy crops: rye, barley, potatoes, root vegetables.
- Subarctic & Extreme Continental
- The world's most extreme temperature ranges. Long, brutally cold winters (6-8 months) and brief, warm summers. Permafrost underlies much of this zone.
- Dfc (Subarctic): Covers more land area than any other climate type -- the vast boreal/taiga belt across Canada, Scandinavia, and Russia. Fairbanks, Alaska (-24 C to 17 C). Yakutsk, Russia (-39 C to 20 C).
- Dfd (Extreme): Eastern Siberia only. Verkhoyansk and Oymyakon contest the title of "Pole of Cold" with recorded lows of -67.8 C and -71.2 C respectively (outside Antarctica). Oymyakon's annual range exceeds 100 C. Despite this, ~500 people live there year-round. The ground is permafrost to depths of 1,500 m.
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Slide 12
Continental Biomes
- Boreal Forest / Taiga
- The world's largest terrestrial biome, stretching across 17 million km2 of northern North America and Eurasia (approximately 29% of the world's forest area). Dominated by coniferous species: spruce, pine, larch, fir. These needle-leaved evergreens are adapted to cold, short growing seasons, and acidic, nutrient-poor soils (podzols).
- Carbon storage: Boreal forests and their underlying soils and peatlands store an estimated 1,100 Gt of carbon -- twice the amount stored in all tropical forests combined. Much of this is in permafrost and peat that accumulated over thousands of years.
- Wildlife: Moose, caribou/reindeer, wolves, brown bears, lynx, wolverines. The boreal is the breeding ground for 1-3 billion migratory birds each spring.
- Threat: Warming at 2-3x the global average. Canadian boreal fires burned 18.5 million hectares in 2023 -- a record. Russian boreal fires routinely exceed this. Permafrost thaw releases methane and CO2, creating a dangerous positive feedback loop.
- Temperate Grassland
- Vast treeless expanses maintained by a combination of seasonal drought, fire, and grazing. Among the most converted and least protected biomes on Earth.
- Major regions:
- North American prairies: Once covered 1.4 million km2 from Manitoba to Texas. Tallgrass (1-3 m, eastern), mixed-grass, and shortgrass zones. Bison herds numbered 30-60 million before the 1870s slaughter. Less than 4% of tallgrass prairie remains -- making it North America's most endangered ecosystem.
- Eurasian steppe: The "Sea of Grass" from Hungary to Mongolia. Genghis Khan's empire was born here. Saiga antelope populations crashed 95% from 1990-2003 due to poaching.
- Argentine Pampas: Among the world's richest agricultural soils. 70% converted to cropland and ranching.
- Soil: Grasslands develop mollisols -- thick, carbon-rich topsoils (chernozem/black earth) from millennia of grass root decomposition. Ukraine's chernozem is called "black gold."
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Slide 13
Polar Climates (E)
- ET - Tundra
- EF - Ice Cap
- ET: Tundra
- The warmest month is 0-10 C. Too cold for trees -- the treeline (often the 10 C July isotherm) marks the boundary between boreal forest and tundra. Growing season of only 50-60 days. Underlain by continuous permafrost (frozen ground year-round).
- Distribution: Arctic coasts of North America, Greenland, Scandinavia, Russia; alpine tundra above treeline on mountains worldwide; sub-Antarctic islands.
- Vegetation: Mosses, lichens, sedges, dwarf shrubs, and wildflowers. Plants hug the ground to escape wind and absorb warmth from the soil surface. Despite harshness, summer brings 24-hour sunlight and brief but explosive blooms -- the Arctic tundra contains ~1,700 plant species.
- Key fact: Arctic tundra permafrost contains ~1,700 Gt of organic carbon -- nearly twice the amount currently in the atmosphere as CO2. As permafrost thaws, microbial decomposition releases CO2 and methane, amplifying warming.
- EF: Ice Cap
- Every month averages below 0 C. Permanent ice cover. Found only in Antarctica (interior) and Greenland (interior). These ice sheets contain 99% of Earth's freshwater ice.
- Antarctica: The coldest, driest, windiest, and highest continent (average elevation 2,500 m). Vostok Station recorded -89.2 C in July 1983 -- the lowest reliably measured air temperature on Earth. The ice sheet is up to 4,776 m thick and contains 26.5 million km3 of ice. If fully melted, global sea levels would rise ~58 m.
- Greenland: Ice sheet covers 1.71 million km2 (80% of the island). Contains enough ice to raise sea levels 7.4 m. Losing ~280 Gt of ice per year (2010-2020), six times faster than in the 1990s.
- Precipitation: Antarctica's interior receives only ~50 mm water-equivalent per year -- technically a desert. Accumulation over millions of years built the ice sheet because virtually no melting occurs.
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Slide 14
Polar & Alpine Biomes
- Tundra Wildlife
- Despite its extreme conditions, tundra supports remarkable animal adaptations:
- Caribou/Reindeer: 3-5 million migrate across North American and Eurasian tundra, the longest land mammal migration (up to 5,000 km round-trip). Calving grounds are on the coastal tundra where insect harassment is lower.
- Arctic fox: Survives -50 C. Winter fur is the most insulating of any mammal. Shifts diet from lemmings in summer to scavenging polar bear kills in winter.
- Snowy owl: Nomadic predator, following lemming population cycles. Can eat 1,600 lemmings per year.
- Muskox: Unchanged since the Pleistocene. Qiviut (undercoat) is 8x warmer than sheep wool by weight.
- Permafrost megafauna: Frozen tundra preserves Ice Age remains -- woolly mammoths, cave lions, ancient horses. A 28,000-year-old preserved mammoth was discovered in 2013.
- Alpine Biomes
- Mountain ecosystems above treeline mirror polar conditions but with key differences: higher solar radiation (especially UV), more precipitation, and steeper environmental gradients.
- Altitudinal zonation compresses multiple biomes into vertical bands. Climbing 1,000 m is climatically equivalent to traveling 600 km poleward. Mount Kilimanjaro (3 S) displays: tropical lowland forest, montane forest, heather/moorland, alpine desert, and glacial summit.
- Sky islands: High-altitude habitats isolated by surrounding lowlands. Species evolve in isolation, producing high endemism. East African mountains, the Tepuis of Venezuela, and the US Southwest's "Madrean Sky Islands" are examples. The Tepuis inspired Arthur Conan Doyle's The Lost World.
- Glacial retreat: Alpine glaciers worldwide have lost ~50% of their surface area since 1850. The Alps lost 6% of remaining glacier volume in the record-breaking summer of 2022 alone. Glacier loss threatens water supply for 1.9 billion people.
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Slide 15
Ocean Currents & Climate
- "The ocean is the great flywheel of climate -- storing and redistributing heat, moderating extremes, and driving the water cycle."
- -- Sylvia Earle, oceanographer
- Thermohaline Circulation
- The "global conveyor belt" -- a system of deep-ocean currents driven by differences in temperature and salinity. Warm surface water flows north in the Atlantic, cools in the Norwegian/Greenland Seas, becomes dense, and sinks to 2-4 km depth, flowing south as North Atlantic Deep Water. The full circuit takes ~1,000 years. This circulation delivers warmth to northwestern Europe and drives global nutrient distribution.
- Concern: Greenland ice melt adds freshwater, reducing salinity and potentially weakening the Atlantic Meridional Overturning Circulation (AMOC). Studies suggest AMOC has weakened ~15% since the mid-20th century.
- El Nino / La Nina (ENSO)
- The most important interannual climate oscillation, affecting weather patterns across half the planet. El Nino: Warm water pool shifts east across the equatorial Pacific, weakening trade winds. Brings drought to Australia and Southeast Asia, floods to Peru and the US Southwest, and suppresses Atlantic hurricanes. La Nina: Cool phase; strengthened trade winds. Opposite effects. Cycles every 2-7 years.
- The 2023-2024 El Nino contributed to the hottest year on record globally (2024 exceeded pre-industrial temperatures by 1.48 C).
- Upwelling Zones
- Where deep, cold, nutrient-rich water rises to the surface, driving extraordinary marine productivity. The Humboldt Current (Peru/Chile) supports 18-20% of the global fish catch from just 0.1% of ocean area. Benguela (Namibia/South Africa), California, and Canary currents are similar.
- Upwelling zones also create coastal deserts: cold water cools air, reducing its moisture capacity. The Atacama (Chile), Namib (Namibia), and Baja California deserts owe their aridity partly to cold offshore currents.
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Slide 16
Altitude & Microclimates
- Altitudinal Zonation
- Mountains compress climate and biome transitions into vertical space. The classic model (from base to summit):
- ZoneAltitude (tropical)Vegetation
- Tierra caliente0-1,000 mTropical lowland forest, agriculture
- Tierra templada1,000-2,000 mCoffee belt, cloud forest
- Tierra fria2,000-3,500 mPotato, wheat; cities (Bogota, Quito)
- Tierra helada3,500-4,500 mParamo grassland, alpine meadow
- Tierra nevada4,500 m+Permanent snow and ice
- This explains why equatorial cities at altitude (Nairobi at 1,795 m, Bogota at 2,640 m, Addis Ababa at 2,355 m) enjoy mild climates despite their tropical latitude.
- Microclimates
- Local conditions that differ from the regional climate due to topography, vegetation, water bodies, or urban surfaces.
- Urban heat islands: Cities can be 1-7 C warmer than surrounding countryside. Dark surfaces absorb solar radiation; buildings trap heat; anthropogenic heat from vehicles and HVAC. Tokyo's average temperature has risen 3 C over 100 years (vs. 1 C globally).
- Lake effect: The US Great Lakes generate intense snowfall on their downwind (eastern) shores. Buffalo, NY, receives 239 cm of snow per year; cities at the same latitude without lake effect get 100 cm.
- Frost hollows: Cold air pools in valley bottoms, creating temperature inversions. Wine growers exploit this -- planting on mid-slope "thermal belts" where cold air drains away.
- Green oases: Parks and forests within cities can be 2-5 C cooler through evapotranspiration and shade.
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Slide 17
Biome Biodiversity Compared
- Biodiversity -- the variety of life at genetic, species, and ecosystem levels -- varies enormously across biomes, generally increasing from poles to equator and from dry to wet.
- BiomePlant Species (est.)Mammal Species (est.)% of Earth's Land% Protected
- Tropical Rainforest~170,000~1,1006-7%~25%
- Tropical Savanna~40,000~350~13%~15%
- Mediterranean~50,000~200~2%~5%
- Temperate Forest~20,000~300~10%~16%
- Temperate Grassland~5,000~120~8%~4%
- Desert~5,000~80~19%~12%
- Boreal Forest / Taiga~3,500~85~17%~12%
- Tundra~1,700~50~6%~22%
- Latitudinal diversity gradient: A single hectare of Amazonian rainforest may contain 300+ tree species; a similar area of boreal forest might hold 5-10. This gradient, one of ecology's oldest observed patterns, likely reflects higher solar energy, evolutionary time, and lower extinction rates in the tropics. But the pattern is not uniform -- temperate grasslands and Mediterranean shrublands punch above their latitudinal weight.
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Slide 18
Soils & Biomes
- Soil is a biome's foundation -- shaped by parent rock, climate, organisms, topography, and time. Different biomes produce characteristic soil types that in turn constrain vegetation and land use.
- Tropical Soils (Oxisols)
- Highly weathered, deep, iron/aluminum-rich, red-colored. Paradoxically poor despite lush forests -- nutrients cycle rapidly through biomass rather than accumulating in soil. Deforestation exposes fragile oxisols to erosion and laterization (hardening into brick-like laterite). Amazon soil loses 80% of its fertility within 3 years of clearing. Slash-and-burn agriculture works only with long fallow periods (15-20 years).
- Grassland Soils (Mollisols)
- Dark, deep, organically rich topsoils ("black earth" / chernozem). Formed under grassland where dense root systems deposit enormous organic matter. The world's most productive agricultural soils. Ukraine's chernozem is 1-2 m deep with 6-16% organic carbon. The US Great Plains mollisols feed half the world. But intensive farming has reduced topsoil depth by 50% in 150 years; Iowa has lost 50% of its topsoil since 1850.
- Boreal & Polar Soils
- Podzols: Acidic, nutrient-leached soils under coniferous forests. Needle litter and cool temperatures slow decomposition, creating thick organic horizons. Gelisols: Permafrost soils of the tundra. Cryoturbation (freeze-thaw cycles) churns soil horizons into chaotic patterns. Active layer (summer-thawed surface) is 0.3-3 m deep. Patterned ground -- stone circles, stripes, and polygons -- forms from repeated freezing.
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Slide 19
Climate Change & Biomes
- Observed Changes
- Arctic amplification: The Arctic has warmed 3-4x faster than the global average since 1979. Sea ice minimum extent has declined ~13% per decade. The Arctic Ocean may be ice-free in summer before 2050.
- Treeline advance: In Scandinavia, Siberia, and Canada, the boreal treeline is shifting poleward at 30-100 m per decade. Shrubs are expanding across the tundra ("Arctic greening").
- Coral bleaching: Ocean warming has caused 4 global mass bleaching events (1998, 2010, 2016-17, 2024). The Great Barrier Reef experienced bleaching across 91% of reefs in 2024.
- Fire regimes: The area burned annually in the western US has increased 4x since the 1980s. Boreal fires are intensifying -- 2023 Canadian wildfire season burned 18.5 million hectares, releasing ~3 Gt CO2.
- Species range shifts: Marine species are moving poleward at ~72 km per decade; terrestrial species at ~17 km per decade. Vegetation zones are migrating upslope 5-20 m per decade.
- Projected Transformations
- Under current warming trajectories (~2.5-3 C by 2100), climate models project dramatic biome shifts:
- Tundra: May shrink 33-50% as boreal forest advances northward
- Boreal forest: Southern boundary retreats; northern boundary advances. Net area may remain similar but composition changes dramatically. Increased fire and drought stress.
- Mediterranean: Expanding drought zones. Parts of southern Spain, Sicily, and North Africa may become too arid for current vegetation.
- Tropical forest: Risk of Amazon "tipping point" -- where drought and deforestation push parts of the forest into savanna state. Some models predict 10-40% dieback under high emissions.
- Permafrost: 30-70% of near-surface permafrost could thaw by 2100, releasing 100-240 Gt of carbon -- an irreversible positive feedback.
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Slide 20
Climate Zones in Motion
- "We are not just changing the climate. We are rearranging the biological furniture of the planet."
- -- Chris Thomas, ecologist, University of York
- Koppen Zones Shifting
- Analysis of 1901-2100 climate data shows Koppen zones are migrating poleward and upslope. Over the 20th century, ~5.7% of Earth's land surface shifted to a warmer Koppen type. Under high emissions (RCP 8.5), 40% or more of land could change Koppen classification by 2100. The fastest-shifting boundary: the tundra-boreal transition in Siberia and Canada.
- Agriculture Follows
- Growing seasons in the Northern Hemisphere have lengthened 10-20 days since 1950. Bordeaux wine grapes now ripen 2-3 weeks earlier than in the 1980s. Corn and soybean cultivation is expanding northward in Canada and Russia. But gains in the north may not offset losses in the tropics: for every 1 C of warming, global wheat yield drops ~6%, rice ~3.2%, maize ~7.4%.
- Winners & Losers
- Expanding: Dry zones (Sahara expanding 10% since 1920). Subtropical climates creeping poleward. Contracting: Polar/alpine zones shrinking. Some temperate forests may become grassland. Emerging: Novel climate combinations with no historical analog may cover 12-39% of Earth's surface by 2100 -- creating ecosystem types that have never existed before.
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Slide 21
Biome Conservation
- Protected Area Coverage
- The Kunming-Montreal Global Biodiversity Framework (December 2022) set a target to protect 30% of Earth's land and sea by 2030 ("30x30"). As of 2024, approximately 17.6% of land and 8.4% of ocean is protected -- but protection is highly uneven across biomes.
- Best protected: Tropical moist forests (~25%), tundra (~22%), mangroves (~26%).
- Least protected: Temperate grasslands (~4-5%), Mediterranean shrublands (~5%), and savannas (~15%) -- ironic given their extreme conversion rates and biodiversity value.
- Key initiatives: The Amazon Region Protected Areas (ARPA) covers 60 million hectares. The High Ambition Coalition includes 100+ countries supporting 30x30. Indigenous and community conserved territories (ICCAs) protect an estimated 22% of Earth's surface, often more effectively than government-managed parks.
- Biome-Specific Threats
- BiomePrimary Threat% Converted
- Temperate GrasslandAgriculture~70-80%
- MediterraneanUrbanization, fire~70%
- Tropical Dry ForestClearing, fire~60%
- MangroveAquaculture, development~35%
- Tropical RainforestLogging, agriculture~30%
- Temperate ForestLogging, urbanization~45%
- TundraClimate change<5%
- Boreal ForestLogging, fire, warming~15%
- Temperate grasslands are the world's most endangered biome by conversion rate, yet receive the least conservation attention and funding.
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Slide 22
Climate & Biomes by the Numbers
- 14.0 C
- Earth's average surface temperature (pre-industrial)
- 1.2 C
- Warming since pre-industrial era (through 2023)
- 990 mm
- Average global precipitation per year
- Major terrestrial biome types (WWF classification)
- Extreme Climate Records
- RecordLocationValue
- Highest temperatureDeath Valley, USA56.7 C (1913)
- Lowest temperatureVostok, Antarctica-89.2 C (1983)
- Wettest place (average)Mawsynram, India11,872 mm/yr
- Driest placeAtacama, Chile~0 mm (some sites)
- Highest wind gustBarrow Island, AU408 km/h (1996)
- Most rain in 24 hrsCilaos, Reunion1,825 mm (1966)
- Biome Carbon Storage
- BiomeCarbon (Gt C)
- Boreal forests + peat~1,100
- Tropical forests~470
- Permafrost (all)~1,700
- Temperate forests~160
- Grasslands~330
- Wetlands~450
- Oceans (total)~38,000
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Slide 23
Life at the Extremes
- Hottest Inhabited Place
- Dallol, Ethiopia (Afar Depression, -130 m below sea level). Average annual temperature of 34.4 C (1960-1966) -- the highest recorded for a continuously inhabited place. Hydrothermal springs create alien-like mineral landscapes of sulfur, salt, and iron oxides. Nearby Lake Afrera produces salt commercially. The Afar people have lived here for millennia despite conditions that regularly exceed 50 C.
- Coldest Inhabited Place
- Oymyakon, Russia (Sakha Republic, 63 N). Population ~500. Official low: -71.2 C (1924, disputed; -67.7 C at Verkhoyansk is the accepted station record). In winter, exhaled breath freezes and falls as "star dust." Cars run 24/7 in winter. School is cancelled only below -52 C. Summer temperatures can reach 35 C -- giving a 100+ C annual range. Permafrost extends to 1,500 m depth.
- Most Extreme Transitions
- Mount Cameroon: The wettest place in Africa (~10,000 mm at Debundscha, at its base) transitions to Sahel steppe just 1,000 km north -- illustrating how rapidly climates shift from equatorial to sub-Saharan Africa.
- Andes: Peru's Pacific coast is hyper-arid (0-20 mm/year); cross the Andes 200 km inland and you reach Amazon rainforest (3,000+ mm/year). No other place on Earth transitions between such extremes in so short a distance.
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Slide 24
Voices on Earth's Systems
- "In every walk with nature one receives far more than he seeks."
- -- John Muir, naturalist (1838-1914)
- "Climate is what we expect; weather is what we get."
- -- Mark Twain (attributed)
- "We do not inherit the Earth from our ancestors; we borrow it from our children."
- -- proverb (often attributed to Native American wisdom)
- "The creation of a thousand forests is in one acorn."
- -- Ralph Waldo Emerson
- "Look deep into nature, and then you will understand everything better."
- -- Albert Einstein
- "A nation that destroys its soils destroys itself."
- -- Franklin D. Roosevelt, 1937
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Slide 25
Further Reading & Resources
- Books
- The Ecology of Climate Change and Biotic Interactions -- Eric Post (2013). How climate change reshapes species interactions across biomes.
- Biogeography: An Ecological and Evolutionary Approach -- Cox, Moore & Ladle (10th ed.). The standard university textbook on global species distribution patterns.
- The Invention of Nature -- Andrea Wulf (2015). Biography of Alexander von Humboldt, who first described climate zones and altitudinal vegetation bands in the early 1800s.
- The Hidden Life of Trees -- Peter Wohlleben. How forest ecosystems communicate and cooperate underground.
- Braiding Sweetgrass -- Robin Wall Kimmerer. Indigenous ecological knowledge meets Western botany.
- Desert Solitaire -- Edward Abbey (1968). Classic meditation on the desert biome of the American Southwest.
- Documentaries & Resources
- Planet Earth (2006) and Planet Earth II (2016) -- BBC. David Attenborough's landmark biome-by-biome survey of Earth's ecosystems.
- Our Planet (2019, Netflix) -- Focuses on climate change impacts across biomes. Narrated by David Attenborough.
- Frozen Planet (2011, BBC) -- Definitive portrait of polar ecosystems.
- Koppen Climate Map (interactive): beck-hpa.github.io/climate -- High-resolution global climate classification at 1 km resolution.
- NASA Earth Observatory: earthobservatory.nasa.gov -- Satellite imagery and data on climate, vegetation, and environmental change.
- WWF Ecoregions: ecoregions.appspot.com -- Map of 867 terrestrial ecoregions within 14 biome types.
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