CLIM 714 Land-Climate Interactions Land Use & Land Cover Change CLIM 714 Paul Dirmeyer.

CLIM 714 Land-Climate Interactions

Land Use & Land Cover Change

CLIM 714

Paul Dirmeyer


LUCC - Land-Use and Land-Cover Change

• LUCC is a program element of both the International Geosphere-Biosphere Programme (IGBP) and the International Human Dimensions Program on Global Environmental Change (IHDP) with 3 foci:

• FOCUS 1: Land-Use Dynamics - Comparative Case Study Analysis

• FOCUS 2: Land-Cover Dynamics - Direct Observation and Diagnostic Models

• FOCUS 3: Regional and Global Models - Framework for Integrative Assessments


•Fire enhancement•Fire suppression•Increased erosion•Decreased erosion•Increased biotic disturbance•Change in consequences of disturbance•Change in susceptibility to physical forces

Disturbance Regimes:


e.g., changes in the hydrology ofthe everglades favors some speciesand hurts others - leading to a changein vegetative structure (in additionto water regimes).

Changes in processes cause many additional

changes.


Scale is the spatial and temporal frequency of a process or structure.

A scale domain is bounded by the grain size of processes detected and the extent or span of processes attended.

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Ecological Scaling


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Forest is patterned across a range of scales.

Larger slower structures usually constrain the behavior of faster smaller scales.

Occasionally change at a small and fast scale spreads up to a larger scale.

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Vegetative Scales


Atmospheric processes occur faster than vegetative processes occurring at the same spatial scale.

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El Niño

fronts

long waves

thunderstorms

climate change

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Vegetative Structures

Atmospheric Processes

Atmospheric Processes


Mesoscale disturbance processes such as fire and spruce budworm outbreaks link the atmospheric processes and vegetative structures.

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Atmospheric ProcessesMesoscale Processes Vegetative Structures

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Disease/pest Outbreaks

Fire

Mesoscale Processes


Anthropogenic disturbance processes such as agriculture, logging, grazing and urbanization can impact vegetation more broadly and quickly than natural causes.

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Atmospheric ProcessesMesoscale Processes Vegetative Structures

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Anthropogenic Processes

Land usechanges

Anthropogenic Processes


Global Crop Cover Change1700 to 1992

Fraction of Grid Cell in Croplands

BIOME 300

The Spread of Agriculture


Global Land Cover Types1700 to 1992

BIOME 300

300 Years of Land Use Change

CLIM 714 Land-Climate InteractionsGoldewijk K and Battjes J.J., 1997

Estimated changes in land use from 1700 to 1995


Point: Area of urban-industrial infrastructure remains small relative to other land-use/cover changes, but its “footprint” has significant land implications.

Elvidge et al., 1997

Night-time data from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System Night-time data from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS)(OLS)

Ecological footprint of cities


Global monitoring can be performed by satellite, if great care is taken to calibrate and validate retrievals.

Estimate of changes in annual NPP 1982-2000


The changes in the equatorial acquisition time of the NOAA satellite platforms

Cross-calibration Across Satellites• Long-term changes occur over periods much longer

than the lives of individual satellites.• Instrument drift (e.g., calibration, zenith crossing times)

and cross-platform differences (e.g. different wavebands, look angles) can complicate long-term monitoring.


Changes in agriculture reflected as NPP changes evident from satellite


Agriculture to urban

Natural vegetation/water to urban

Agriculture/natural vegetation to water

Water to agriculture

Landsat 1988–96

(K. Seto, Boston U.)

Urban expansion into “prime” agricultural land (China)


1984 1992

Notice not only the spread of urbanization, but also the loss of wetlands, and the shift of agriculture to consume forest areas as cities spread into farmland.

Land use change in northern Delaware


Mid-Latitude Case Study = Aral Sea


Aral Sea Background Info:

• Was once the fourth largest lake on the planet• Supported an ecosystem of plants and wildlife as well as a habitat

for humansCauses of decline:1960- Water Transfer Project begun

o Diverted large amounts of irrigation water from Amu Darya and Syr Darya

o World’s longest irrigation canal (800 miles)o Water supplied for region’s crops production; cotton, vegetables, fruit,

and riceo Water diversion combined with frequent droughts

Consequences:Ecological, economic, and health disasters

o 1995- ¾ water volume lost, surface area shrank by ½o Salinity has tripled o 100 million tons of salty dust dispersed outward up to 190 miles awayo Pollution of air, drinking water, and soilo 2 million ha of fertile land removed from agricultural processes o Amu Darya and Syr Darya are now mere trickles o Former lake bottom is now a human made salt dessert


Aral Sea Background Info Cont.Climate Changes:

Longer, colder wintersShorter, drier summersGrowing season shortened to 170 daysPrecipitation decreased 10x along shore regionsSalt rain

Effects of Salt:Kills crops, trees, and wildlifeDestroys pasture landsCotton and crop yields have declined dramatically Fishing industry devastated (twenty of twenty-four native species extinct)Roughly ½ of area’s bird and mammal species gone

Complicating Factors:To raise yields, farmers increase use of herbicides, insecticides, fertilizersMany of the chemicals have accumulated in the ground waterLow river flows have concentrated salts, pesticides, toxic chemicals. Surface water unfit to drink


Aral Sea Landsat Images:

1977 1984 1989 1995


Aral Sea Landsat Images

1964 1973 1987

1997 1999


Images of the Aral Sea

Former fishing village – now enveloped in saline sand

Stranded fishing boat currently miles from

the nearest water.


Groundwater Pumping

1942

today

Not only surface water diversion leads to desertification. Pumping of groundwater to supply the city of Tucson, Arizona has lowered the water table over 60m in some locations, causing creeks to run dry, and riparian vegetation to die out, greatly reducing local evapotranspiration.


Subsidence

Venice is not the only city sinking into the sea. Houston is subsiding due to groundwater, gas and oil pumping.

1906-1995


Deforestation


Some facts about deforestation

• More than 8 million km2 of forest (all latitudes) have been cleared globally, about half of it in this century alone.

• Half of the world's population live in less developed countries in the tropics (between 23°N and 23°S), where deforestation is occurring the fastest.

• Tropical forests are being lost at a rate of 2-3% per year.

• 10% of global terrestrial net primary production (vegetative growth) occurs in the Amazon Basin alone.


Background Information:

Tropical Case Study: Deforestation in Rondonia, Brazil

•In the 1970’s and 1980’s landless peasants rushed into the rain forest under Brazilian government's law which declared ownership to anyone who cleared the land and put it to effective use. Using “slash and burn” methods they quickly destroy forests.

•Land was unsuitable for farming (most tropical soils are too poor), so peasants would have to move and clear new land every 2-4 years to continue subsistence farming.

•Ranchers moved in to claim the abandoned farms for grazing, consolidating small farms into large tracts with additional burning. Reburning every 4-5 years is necessary to keep the land clear of woody vegetation that would choke out grasses.

•23 of the 28 largest landowners in Brazil have their immense estates in the Amazon region covering more than 60 million acres.


Rondonia, Brazil—Slash & Burn


Forest converted to rangeland –

grasses maintained by

periodic burning

Slash-and-burn clearing of rainforest. Erosion is also enhanced (background)


1986

Landsat TM imagery over Rondonia showing progressive deforestation along roads in “fishbone” pattern

1975

1992





The major cities of Brazil, Uruguay, Paraguay and Argentina are downwind of

the Amazon


Southeast Asia

Forest cover 1973


Southeast Asia

Forest cover 1985


FAO Global Forest Resources Assessment 2000

(FRA2000) Central Africa

Country Total Forest 1990(% of total land

area)

Total Forest 2000(% of total land

area)

Forest Cover Change

1990 –2000(% annual rate)

Dem. Rep. Congo

62 60 - 0.4

Congo 65 65 - 0.1

Cameroon 56 51 - 0.9

Benin 30 24 - 2.3

Ivory Coast 31 22 - 3.1

Guinea 30 28 - 0.5


Scenarios of Land Cover Change

22

58

34

26

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50 55

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1961 1995 2025 2050

% T

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Central Africa Land Cover Change 1960-2050


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47% global lossforest cover [past 8000 yrs]

25% of landsurface remainsin forest

200 m halost in LDC[10%]

20 m hagained inDW

Forest-Cover ChangeForest-Cover Change

% Amount/Change

Loss/GainHa 1980-95

Angelsen, in press; WRI 1998; FAO 1999

55% of forestin LDC


Copper Mountain,Colorado

IkonosFalse Color

Deforestation and (sub)urbanization in the developed world as well.


Long-term land-cover change in the Belgian Ardennes

Petit and Lambin, Int. J. GIS, 2001

CLIM 714 Land-Climate InteractionsPetit and Lambin, Int. J. GIS, 2001

Land-cover changes in Lierneux: 1775-2000

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Proportion(%)

grassland-cropland

coniferous

wet meadows

heath

deciduous

deciduous-coniferous

Long-term land-cover change in the Belgian Ardennes


Near the Equator, the linear, steady-state low-level anomalous flow in response to an anomalous heat source Q can be described by:

u = zonal wind componentv = meridional wind componentp = surface pressuref = Coriolis forceε = damping term (friction)

(Gill 1980)

Q may come from either an anomaly in the atmosphere (e.g. precipitation anomaly), or from an anomaly at the surface (e.g. surface temperature).Deforestation changes the surface conditions, altering surface heating, which can affect the overlying atmospheric circulation, inducing further anomalies there.

Tropical Deforestation & Climate


Simple Model of DeforestationMost simply, heating in the tropical atmosphere might be

changed by perturbations in precipitation and surface temperature:

(Eltahir and Bras 1993)

P = precipitation anomalyTS = surface temperature anomaly

Deforestation induces counteracting mechanisms that affect these quantities:

The net effect will depend on the magnitude of each of the individual effects. These are often not easy to measure or predict.

Change Decreased roughness

Increased albedoDecreased evaporation

Affect on TS↑↓↑

b:


bT:

aP:

aP+bT:

Linear estimation of deforestation impacts


Albedo & Deforestation

• Deforestation with an albedo = rainforest (D0); 6% lighter (D6); and 9% lighter (D9).

• Dark grassland → net increase in rainfall.

• Light grassland → net decrease.

• Pattern of rainfall change is consistent.

Dirmeyer & Shukla (1994 JGR)


Tanajura et al. (2000) regional model of deforestation

Variation among ensemble members like that for weather and climate prediction – remember observations are effectively one ensemble member!


Tanajura et al. (2000) regional model of deforestation


Tanajura et al. (2000)


Some Desertification Statistics


Monsoon region sensitivity

•Sensitivity experiments of desertification show that monsoon regions are most sensitive to impacts of land use/cover change…

Dirmeyer & Shukla (1996 QJRMS)


Rainfall Impacts

•The largest impacts are in the monsoon regions of Africa (Sahel and South Africa).

•Second are the land-sea monsoons of South Asia, Australia and North America.

•Tropical rainfall intensifies to offset the loss in the subtropics.

Dirmeyer & Shukla (1996 QJRMS)


Rainfall Impacts 2

•Impacts over Africa are year-round.

•Asia, Australia, S. America have rainfall decreases during summer only.

•North America shows an increase in rainfall.


Sahel Desertification•Observed patterns of precipitation change were modeled in a GCM by changing regional vegetation to reflect desertification (Xue and Shukla, 1993 J. Climate).

•Did overgrazing cause climate change? Did climate variability cause desertification? Feedbacks???


Land Cover Change and Subtropical Climate

• Are observed rainfall trends (~10% in 80 years) due to large-scale land use change? (Pielke et al 1999; Marshall et al. 2004)


Changes in Florida Land Use

• Agriculture and urbanization are the main influences on LUCC in this region – Large losses of forest and wetlands (Everglades).


Regional Modeling of LUCC Impacts

Model suggests 12% decrease/100 years, commensurate with observations – but what else has changed?

CLIM 714 Land-Climate InteractionsGeist & Lambin, 2002

Modeling the human element


Merging our “Physical” Models with Economic, Policy and Decision Support Models – the Next

Frontier


Historical Climate Change in the Mediterranean Basin – the Role of Vegetation Feedbacks

The MotivationNorthern Africa in Roman Times was considered one of the most prosperous and rich areas of the western world. The production of wheat, olive oil, and wine was greater than in Mediterranean Europe. Strabo (I century C.E.) and other classical authors describe northern Africa as a strip of vegetated land, and place the northern border of the desert a several hundred kilometers to the south of the sea. In present times, most of the coastal regions of northern Africa are sub-desert or desert. Pliny (I century C.E.) speaks of elephants living to the south of the Atlas range, in an area that is now desert; Ptolemy (II century C.E.) describes summer thunderstorms in Alexandria, where now summers are dry. Archeology confirms the presence of heavy agricultural activity in areas which are now classified as hyper-arid. Modern palynology has provided evidence of a trend towards drier conditions throughout the entire Mediterranean region.

In the numerical experiment, modern vegetation was replaced by forests and grasslands in the hatched areas, consistent with evidence from the Roman Classical Period (ca. 2000 y.b.p.)Reale & Dirmeyer;Reale & Shukla,(2000 Glob. Planet. Change)


Historical Climate Change in the Mediterranean Basin – the Role of Vegetation Feedbacks

The model experimentA sensitivity test with a low-resolution general circulation model reveals that the position of the Inter-Tropical Convergence Zone (ITCZ) is sensitive to changes in surface properties far to the north, around the Mediterranean region (Reale and Dirmeyer, Glob. Plan. Ch. 2000). Reale and Shukla, (Glob. Plan. Change, 2000) quantify the response of a climate model with respect to the land surface conditions of two millennia ago. These are inferred mostly from palynological studies. The experiments indicate a change in the general circulation of the atmosphere: namely a northward shift of the ITCZ over eastern Africa, and a land-sea circulation similar to a small-scale monsoon occurring between the Atlas range and the Mediterranean. These changes benefit, with a significant increase in precipitation, the Nile Valley and the Atlas range, which were two of the most agriculturally productive regions of the Roman world. Thus, the experiment suggests that the large-scale clearings that occurred in the Late Antiquity and during the Middle Ages, may have contributed to the dryness of the present climate.

Simulated summer rainfall is substantially greater over the Nile Valley and in the vicinity of the Atlas Mountains when modern vegetation distributions are replaced by the vegetation of the Roman Classical Period.

Reale & Dirmeyer;Reale & Shukla,(2000 Glob. Planet. Change)


So When Did LUCC Impacts Start?

• Recent work by Ruddiman (2003) suggest that it may have been some 8000ybp.


When did LUCC Impacts Start?

• Ruddiman suggests that human activities started increasing CO2 8Kybp (start of forest clearing) and CH4 5Kybp (rice farming). These events prevented an ice age that would have naturally occurred as a function of changing orbital parameters.


LUCC Summary•Humans have altered the vegetation landscape on a large scale for agricultural (crop cultivation, grazing of livestock) and other economic purposes (fuel/firewood, urbanization, “reclamation”, etc.).•Degradation occurs in humid climates (deforestation) and arid climates (desertification).•Changes in water resource use can have unintended consequences on vegetation.•Modeling studies suggest large-scale land use change can have an affect on regional climate.

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CLIM 714 Land-Climate Interactions Land Use & Land Cover Change CLIM 714 Paul Dirmeyer.

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