Human-Induced Changes

Climate and Global Change Notes

27-1

Human-Induced Changes

Examples

• Aral Sea

• Florida Everglades

• Southwest Australia


27-2

Changes in Aral Sea

NOAA-AVHRR Image (August 1991)

• Sea is split between the Republics of Kasachstan to the north and Karakalpakistan in the south

• Karakalpakistan is an autonomous republic within the Republic of Usbekistan

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Caspian Sea

Aral Sea

Syr-Dar’jaRiver

Amu-Dar’jaRiver

Irrigatedland

http://www.dfd.dlr.de/app/land/aralsee/noaa_avhrr.html


27-3

Changes in Aral Sea

August 6, 1985 Space Shuttle Picture Aral Sea

• A closed system, evaporation is replaced mainly by two rivers, the Syr-Dar’ja and Amu-Dar’ja

• River sources are glaciers high up in the Hindu Kush and Pamir Mountains to the southeast

• Increase in irrigation and diversion of the two tributary rivers has made dramatic changes

• Most of this diverted water used to irrigate cotton


27-4

19871973

1997

Changes in Aral Sea

http://edc.usgs.gov/earthshots/slow/Aral/Aral

Changes 1973-1997

• From the mid 50s until the late 80s, the supply of water dropped from 25 km3/yr to less than 5 km3/yr


27-5

Changes in Aral Sea

http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17002

Changes 1988-2005

• 1988 - Note the arrow-shaped

island in the Aral Sea -

island is 35-km long- Deep blues and

greens indicate the water-

covered areas

• 1996 - Intermediate image

• 2005 - Island is now part

of mainland

• Kazakhstan government began

to increase river inflow in 2003,

it will be years before sea

levels begin to rise

QuickTime™ and aTIFF (Uncompressed) decompressor



27-6

Changes in Aral Sea

Changes 1960-1998

• Lost more than 60% of its area and approximately 80% of its volume (until 1998)

• Sea level has dropped about 18 m in the same time period

• Former fourth-largest lake in world is now the world's eighth-largest lake

• Total collapse of the fishing industry (originally 44,000 t/a)

http://svs.gsfc.nasa.gov/vis/a000000/a003100/a003112/

Evaporation of the Aral Sea using Landsat imagery from 1973, 1987, and 2000

QuickTime™ and aYUV420 codec decompressor



27-7

Changes in Aral Sea

Changes 1960-1998

• Sea's salt concentration increased from 10% to more than 23%, contributing to the devastation of a once thriving fishery

• Local climate shifted to hotter, drier summers and colder, longer winters, i.e., mesoclimate changed to more of continentality

• Increase of salt and dust storms

• Shortening of the vegetation period

• Decrease of productivity of agricultural fields

http://www.dfd.dlr.de/app/land/aralsee/chronology.html


27-8

Changes in Aral Sea

Changes 2005-2006

• World Bank funded a dam to separate smaller, less polluted and salty northern Aral Sea from southern part

• Dam completed summer of 2005

• Moderate Resolution Imaging Spectroradiometer (MODIS) images show changes

- Ice both images- Channel wider - Expanded pool of shallow,

sediment-clouded water- Former shorelines of the lake

appear paler brown; shallower

2006

2005

http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17241


27-9

Changes in Aral Sea

Dust Storm Over South Aral Sea

• MODIS image on June 13, 2006

- North Aral Sea

- Lake still surrounded by its dried-up lakebed

- Dust is very light in color

http://earthobservatory.nasa.gov/NaturalHazards/

shownh.php3?img_id=13648

NPR Storyhttp://www.npr.org/templates/story/story.php?storyid=14853942


27-10Changes in the Florida

EvergladesHistoric Flow

• Water from central Floridamoved southto LakeOkeechobeeand then south to and east to the ocean and Gulf



Everglades“Improving” Nature



EvergladesPresent Challenges for the Everglades

• Water management- Reduction of wetlands- Many animals are specifically adapted to the

alternating wet and dry seasons

• Water quality- Water runoff from farms brings excess

nitrates and phosphates into the park

• Non-native species- Native trees, such as mangroves and

cypress, are being replaced by exotic species- Numbers of wading birds nesting in colonies

(rookeries) in the southern Everglades have declined 93% since the 1930s

• Explosive regional population

http://www.nps.gov/archive/ever/eco/threats.htm

Before

After



EvergladesRestoration Project


27-14Changes in Southwest

AustraliaBunny Fence

Southwest Australian region has been subject to considerable land use change since late 1800s, with an estimated 13 million hectares of native vegetation removed for agricultural purposes

Currently a 750 km rabbit proof fence separates the croplands along the Southwest coast from native vegetation in the continental interior

http://www.nsstc.uah.edu/~nair/BUFEX05/study_area.html




Due to the high contrast in albedo between the croplands and native vegetation, the boundary separating these areas is a prominent feature in the satellite images for this region

Environmental impacts of land use change in this region include alteration of subsurface water storage, regional climate and local hydrology. Extensive removal of native vegetation with deep roots has lead to rising of the water table with the end result of increased salinity in surface soil and associated decrease in agricultural productivity




Rising soil salinity poses a serious threat to agricultural productivity in the future and has serious economic consequences

Several studies show connections between land use change and regional climate of this region

A 20% decrease in rainfall has been reported in this area following substantial clearing of native vegetation, but is not completely clear if the decrease in rainfall is linked to changes in land use




Documents

Human-Induced Changes