Ten years of land cover change on the California coastdetected using Landsat satellite image analysis: Part 2—SanMateo and Santa Cruz counties

Christopher Potter

Received: 13 May 2013 /Revised: 1 July 2013 /Accepted: 3 July 2013# Springer Science+Business Media Dordrecht (outside the USA) 2013

Abstract Landsat satellite imagery was analyzed to generatea detailed record of 10 years of vegetation disturbance andregrowth for Pacific coastal areas of San Mateo and SantaCruz Counties. The Landsat Ecosystem Disturbance AdaptiveProcessing System (LEDAPS) methodology, a transformationof Tasseled-Cap data space, was applied to detected changesin perennial coastal shrubland, woodland, and forest coverfrom 1999 to 2009. Results showed several principal pointsof interest, within which extensive contiguous areas of similarLEDAPS vegetation change (either disturbed or restored)were detected. Regrowth of evergreen shrub and tree coverwas prevalent along the several long stretches of the coasthighway (CA Route 1) between the cities of Half Moon Bayand Santa Cruz. A number of state parks areas showed mea-surable vegetation restoration as well. The most prominentloss of perennial coastal vegetation over decade was in thePescaderoMarsh area, where the continued presence of leveeshas historically reduced flood conveyance capacity into andthrough the marshlands. Based on these examples, theLEDAPS methodology was determined to be capable of ful-filling much of the need for continual, low-cost monitoring ofemerging changes to coastal ecosystems.

Keywords Landsat . Coastal vegetation . Disturbance .

Regrowth . Restoration

Introduction

Northern California’s coastal ecosystems include sandy beaches,steep bluffs, rocky headlands, evergreen forests, coastal scrub-lands, grazed rangelands, native grasslands, intertidal zones,

wetlands, lagoons, and other diverse shoreline types. Coastaldevelopment has been accompanied by major investments inpublic infrastructure, including roads, airports, and harbors. Anetwork of state and federal parks run along the shoreline tosupport a popular recreational sector (Kildow andColgan 2005).

Degradation due to coastal erosion can have many nega-tive effects on coastal developments and wildlife habitats(California Beach Erosion Assessment Survey CBEAS 2010).Dams and debris basins, channelized rivers and streams, hard-ened shorelines, and vegetated areas converted to impervioussurfaces may further alter sediment provided to the shoreline.Improved inventories of coastal ecosystem change are neededprovide a sound geographic basis for decision making onhabitat protection in the face of future climate and projectedsea level changes of nearly one foot rise by mid-century, andthree or more feet (1-meter) by the end of the century(Rahmstorf 2007; Hanak and Moreno 2012). Frequent andmore powerful waves during winter storms may acceleratecoastal erosion and shoreline retreat.

In this study, Landsat satellite imagery was analyzed fromthe years 1999 and 2009 to provide a detailed record of10 years of vegetation disturbance and recovery for Pacificcoastal areas of San Mateo and Santa Cruz counties. Theanalysis of Landsat imagery over time to map all potentialchanges in land cover along the coastal zone at a regionalscale is presented as a case study approach to detect andcategorize multiple agents of change simultaneously, includ-ing coastal erosion, wildfire, invasive species, and human-induced restoration or development. The methods used areapplicable to any coastal zone in the world where cloud-freeLandsat imagery can be obtained.

Regional geography and study area

The Pacific coast of San Mateo and Santa Cruz counties ispopulated with numerous wildlife reserves and watersheds

C. Potter (*)NASA Ames Research Center, Mail Stop 232-21, Moffett Field,CA, USAe-mail: chris.potter@nasa.gov

J Coast ConservDOI 10.1007/s11852-013-0270-3

that are managed mainly for conservation. These protectedlocations include the Fitzgerald Marine Reserve, PigeonPoint Light Station, Ano Nuevo State Reserve, DavenportBluffs, and the Mid-Peninsula Regional Open Space Districtproperties. Residential developments of the cities of HalfMoon Bay and Santa Cruz offer recreational opportunities.Numerous seaside croplands operate on a year-round basisalong coastal terraces between the two main cities.

Methods

The LEDAPSDisturbance Index (DI) was described byMaseket al. (2008) as a transformation of the Landsat Tasseled-Capdata space (Crist and Cicone 1984; Huang et al. 2002; Kauthand Thomas 1976), specifically designed for sensitivity toperennial shrubland, woodland, and forest cover change. TheTasseled-Cap brightness, greenness, and wetness indices arestandard transformations of the original Landsat spectralbands, effectively capturing the three major axes of spectralvariation across the solar reflective spectrum. As demonstratedby Healey et al. (2005), the DI is a simple and effective meansof tracking vegetation disturbance across ecosystems dominat-ed by perennial cover types. Unlike simple visible/near-infra-red indices (e.g. the Normalized Difference Vegetation In-dex—NDVI), the LEDAPS DI incorporates Tasseled-Capwetness, thereby including information from the shortwaveinfrared wavelength, which was shown to be valuable forassessing changes in perennial vegetation structure (Cohenand Goward 2004).

The LEDAPS DI quantifies the normalized spectral dis-tance of any given pixel from a nominal “dense woodyvegetation” class to a “bare soil” class. The DI is calculatedusing the Tasseled-Cap (brightness–greenness–wetness) in-dices for Landsat images (Kauth and Thomas 1976):

DI ¼ B0– G0 þW 0ð Þ ð1Þwhere B′, G′, and W′ represent the Tasseled-Cap brightness,greenness, and wetness indices normalized by a densewoody vegetation index result identified for each Landsatscene. For example:

B0 ¼ B–μBð Þ=σB ð2Þwhere μB is the mean Tasseled-Cap brightness index of thedense woody vegetation class for a particular Landsat scene,and σB is the standard deviation of brightness within thedense woody vegetation class for that same scene. In effect,the DI measures the spectral distance of a given pixel fromthe dense woody vegetation “centroid” for that scene, inunits of within-class standard deviation. Since LEDAPS DIvalues are based on the statistics of woody vegetation coverreflectance from individual scenes, the DI is relatively

insensitive to variability in solar geometry between scenes,and lessens the effect of seasonal vegetation variability amongLandsat image dates.

Given the population of mature perennial vegetation pixelsidentified from recent land cover map products, the mean andstandard deviation of each Tasseled-Cap component for theclass were calculated. Each Tasseled-Cap image plane was thennormalized as in Eqs. (1) and (2). The difference in DI (ΔDI)was next calculated between 1999 and 2009. Large positivevalues of ΔDI have been shown be associated with a majordisturbance event such as wildfire, whereas large negativeΔDIvalues frequently correspond to regrowth of perennial woodyvegetation following disturbance (Masek et al. 2008).

Thresholds were next applied to the ΔDI values to iden-tify the highest probable areas of ecosystem disturbance orvegetation regrowth/restoration. TheseΔDI thresholds weredetermined using wildfire perimeter boundaries mapped onan annual basis by the California Department of Forestry,Fire and Resource Assessment Program (FRAP), with con-tributions from the USDA Forest Service, the Bureau ofLand Management, and the National Park Service (dataavailable at http://frap.cdf.ca.gov/). Manual adjustments ofthese thresholds were carried out across Central California tooptimize the spatial correspondence between ΔDI for areasburned by wildfire before 1999 (regrowth pixels) and thoseburned between 1999 and 2009 (disturbed pixels).

Since short-term land use transformations may be inadver-tently identified by ΔDI, particularly agricultural rotation pat-terns and fallowing of cropland, we routinely excluded theseannual transitions for further evaluations by screening LEDAPSresults with a cropland/non-cropland mask based on USDANational Agricultural Statistics Service (NASS), CaliforniaCropland Data Layer (CDL) from 2010 (available at http://nassgeodata.gmu.edu/CropScape). The CDL is a raster, geo-referenced, crop-specific land cover data layer with a groundresolution of 30m. The CDL is produced using satellite imageryfrom the Indian Remote Sensing RESOURCESAT-1 (IRS-P6)Advanced Wide Field Sensor (AWiFS) collected during thecurrent growing season. Additional land cover maps were usedas zonal layers for classifying LEDAPS results, including: theUnited States Geological Survey (USGS) National ElevationDataset (NED), the USGS National Land Cover Database2001, and the National Aeronautics and Space Administration(NASA) Moderate Resolution Imaging Spectroradiometer(MODIS) 250-meter resolution 16-day Normalized Differ-ence Vegetation Index (NDVI) composites.

Results

Changes in perennial vegetation cover between 1999 and2009 from LEDAPS analysis in San Mateo and Santa Cruzcounties were mapped as red shaded pixels for disturbed

C. Potter

vegetation cover, and as blue shaded pixels for regrowing orrestored vegetation cover (Fig. 1). Five principal points ofinterest, each with extensive contiguous areas of similarLEDAPS vegetation change (either disturbed or restored),were identified for further analysis in the sections that follow.

Pillar Point marsh and bluffs

LEDAPS results for the Pillar Point area (37.4989 N,−122.4982 W; Fig. 2) included changes in the FitzgeraldMarine Reserve (FMR), Mavericks Beach and the marsh

areas, the Peninsula Open Space Trust’s (POST) Pillar PointBluff, and Denniston Creek drainage to the east of Pillar Pointand south of the town of El Granada. Restoration or regrowthof perennial shrub and woodland vegetation was detectedextending from Mavericks Beach to the Denniston Creekand Deer Creek beach outlets into Princeton Harbor. Distur-bance of perennial vegetation cover was detected in FMR andacross parts of Pillar Point Bluff above the shoreline.

Pillar Point Bluff drains directly into FMR, where marinemammals populate the shoreline. To the east, wetlands andmarsh areas provide habitat for at-risk species such as the

Fig. 1 Results from LEDAPS analysis of Landsat imagery (30-meterpixel resolution) in 1999 and 2009 in San Mateo and Santa Cruzcounties. Red shaded pixels were detected as disturbed vegetation,whereas blue shaded pixels were detected as regrowing or restored

vegetation. Roman numerals identify selected points of interest exam-ined in subsequent figures. I Pillar Point Marsh, II Purisima Creek, IIIPescadero Marsh Natural Preserve, IV Ano Nuevo State Reserve, VDavenport Landing

Land cover change on the California coast

California red-legged frog and San Francisco garter snake.The Peninsula Open Space Trust (POST) purchased themajority of the 140-acre Pillar Point Bluff property in2004, and added other parcels in 2007 and 2008. Before theproperty was transferred to San Mateo County Parks in 2011,POST volunteers carried out extensive restoration projects onthe land, including removing invasive Pampas grass, re-routing hiking paths away from eroding slopes, and reseedingbare patches of bluff top with native plants (California CoastalConservancy 2004). POST also removed the crumbling foun-dation of a former dairy barn and restored abandoned irriga-tion ponds used by seasonal birds and resident wildlife.

It appears from the 1999 to 2009 LEDAPS results that muchof the POST restoration effort on Pillar Point Bluff was stillregrowing as perennial shrub vegetation cover in 2009. Basedon site visits and first-hand visual observations by the author in2013, there appeared to be slow but substantial recovery ofperennial plant cover around the re-routing hiking paths on theBluff. However, the majority of the Bluff area was vegetatedwith young evergreen conifer trees and appeared to be filling inas a dense coastal forest, similar to the regrowing woodlandsthat cover the Denniston Creek drainage to the east (Photo 1).

Denniston Creek is a spring-fed drainage that originates insteep hills of Montara Mountain in the northern section of theSanta Cruz Mountain Range, and then flows through a lower-gradient rural valley and suburban area before it empties intoPrinceton Harbor. Willow-alder riparian forest is the main typeof riparian plant community found throughout DennistonCreek. The tree overstory is dominated by arroyo willow (Salix

lasiolepis) and red alder (Alnus rubra). There are also occa-sional stands of Monterey pine (Pinus radiata) and blue gumeucalyptus trees (Eucalyptus globulus). The LEDAPS resultsshowed that overall evergreenwoodland cover in theDennistonCreek drainage has increased notably between 1999 and 2009.

The Pillar Point marshlands and lagoon showed nearly2.5 ha of regrowth in perennial wetland plant cover between1999 and 2009 (Photo 2). The marsh is divided into fresh andsalt-water environments by an old earthen dam topped by the

Fig. 2 Overlay of LEDAPS results for the Pillar Point Marsh area(Point I in Fig. 1) onto NLCD land cover types. Lighter blue and redLEDAPS shades are shown on shrub and woodland vegetation (overtan-colored NLCD areas), whereas darker blue and red shades are showon dune and herbaceous cover (over green-colored NLCD areas).Creeks are shown in dark blue lines, roads as dashed lines

Photo 1 Denniston Creek drainage near Pillar Point

Photo 2 Pillar Point marshlands and lagoon

C. Potter

raised roadbed. Regrowth of tree cover on the steep cliffs abovethe marshland, on the east side of the Pillar Point Air ForceStation property, was also detected by LEDAPS analysis.

Purisima Creek

LEDAPS results for the Purisima Creek drainage area(37.4057 N, −122.4060 W; Fig. 3) included cover changesnear the historic Purisima townsite at the juncture of High-way One, Verde Road, and Purisima Creek Road, approxi-mately 1.5 miles (2.4 km) south of the city limits of HalfMoon Bay. Regrowth of perennial woodland vegetation wasdetected on about 34 ha on the south side of Purisima CreekRoad, whereas disturbance of perennial vegetation cover waswidespread over nearly 100 ha on the north side of PurisimaCreek Road. Based on site visits and first-hand visual obser-vations by the author in 2013, there appeared to be extensiveevergreen woodlands and forest along the south side ofPurisima Creek (Photo 3). Rangeland and sparse shrub coverwas observed on the north side of Purisima Creek (Photo 4).

About 5 km inland, Purisima Creek Road provides accessto nearby parkland at the Mid-Peninsula Regional OpenSpace District’s Burleigh-Murray State Park and PurisimaCreek Redwoods Open Space Preserve. LEDAPS resultsshowed little or no vegetation cover change in either of thesePOST protected properties from 1990 to 2009 (not shown inFig. 3). Other areas detected with LEDAPS regrowth ofperennial vegetation on the coast north of Purisima CreekRoad include croplands bordering the Arroyo Canada Verdedrainage and the Half Moon Bay Golf Links (Fig. 3). Thegolf courses were first built in 1973 and then renovated in2006, which may account for the detection of higher perennialvegetation cover by 2009.

Pescadero Marsh Natural Preserve

Pescadero Marsh Natural Preserve (PMNR), a part ofPescadero State Beach (37.2674 N, −122.4108 W), is theonly extensive wetland along the Pacific coast of the SanFrancisco peninsula. The preserve at the confluence of

Fig. 3 Overlay of LEDAPSresults for the Purisima Creekarea (Point II in Fig. 1) ontoNLCD land cover types

Land cover change on the California coast

Pescadero Creek and Butano Creek includes tidal estuary,freshwater marsh, brackish water marsh, open water (ponds),dense riparian woods, and northern coastal scrub (Photo 5).The marshland an important wintering ground for waterfowlon the Pacific Flyway. PMNR provides essential habitat forrare, threatened and endangered species such as the brackishwater snail, the red-legged frog, the San Francisco gartersnake, black and clapper rails, the tidewater goby, silver(coho) salmon, and steelhead trout. Nevertheless, diking,

channelization, reclamation, and excessive sedimentationhave dramatically altered the size and character of PescaderoMarsh over the past 150 years. The magnitude and frequencyof winter flooding has increased over the past few decades,presumably as a result of the decreased channel capacity ofButano Creek.

LEDAPS results for the PMNR showed a widespread lossof perennial vegetation cover from 1999 to 2009 (Fig. 4).Whilethe exact causes of this decline in marsh vegetation wereunknown, the presence of levees has reduced flood conveyancecapacity into and through the marshlands at PMRN, such thataltered tidal inundation during low flow periods may be par-tially responsible for declining evergreen plant cover. Vegeta-tion surveys in 2002 (Environmental Science Associates ESA2008) also detected the appearance of an invasive weed, poisonhemlock (Conium maculatum), at 6 % cover.

To the north of Pescadero State Beach, site visits by theauthor in 2013 observed numerous cases of deep gully erosionon the grazed coastal hills and pasture lands (Photo 6;37.29504 N, −122.40354W). This gullying has been attributedto historical land use practices, including potato farming on thesteep coastal slopes (Curry et al. 1985). However, loss ofgrassland cover associated with this gullying was not detectedby LEDAPS results as a recent disturbance (1999 to 2009),whichmay indicate that hillslope soil erosion has been a notableproblem for the past several decades for this section of the coast.

Ano Nuevo State Reserve

LEDAPS results for the Ano Nuevo State Reserve area(37.1174 N, −122.3271 W; Fig. 5) detected extensive

Photo 3 South side of Purisima Creek

Photo 4 North side of Purisima Creek

Photo 5 Pescadero Marsh Natural Preserve

C. Potter

restoration and regrowth of perennial shrub and woodlandvegetation throughout neatly 200 ha of the main Wildlife

Protection Area from Table Rock in the north to Ano NuevoPoint and Cove Beach in the south. Another nearly 40 ha wasdetected as restoration and regrowth of perennial vegetationnear Franklin Point, about 5 km northwest of Ano NuevoPoint. Ano Nuevo Island was detected with restoration ofperennial vegetation as well.

A small area (about 5 ha at (37.1403 N, −122.3380) ofdisturbed perennial vegetation cover was detected along theCascade Creek Trail of the Park, near what appeared to be anburned area with charred woody material (Photo 7). Basedon site visits and first-hand visual observations by the authorin 2013, this was confirmed to be an area of burned woodymaterial from a recent fire. The California State Parks furtherconfirmed that they manage a long-term burn plot at thislocation (T. Hyland, personal communication), and has setcontrolled fires this area every other year for nearly to20 years.

Davenport Landing

LEDAPS results for the Davenport area (37.0104 N,−122.1963 W; Fig. 6) on north coast of Santa Cruz Countyinclude extensive regrowth of perennial shrub and woodlandvegetation all along the coast, from Liddell Creek in the

Fig. 4 Overlay of LEDAPSresults for the Pescadero Marsharea (Point III in Fig. 1) ontoNLCD land cover types

Photo 6 Satellite view of the coastal hills north of Pescadero State Beach

Land cover change on the California coast

south, north to Scotts Creek Marsh. Davenport Landing andthe San Vicente Creek drainage are protected by a publicaccess easement. Acquired by the Land Trust of Santa CruzCounty in 2001, the easement comprises five areas accessiblefrom the Southern Pacific right-of-way and CA Route 1 in thevillage of Davenport.

Disturbance of perennial vegetation cover was detected inthe Davenport area by LEDAPS analysis only in areas pres-ently used for croplands on the coastal terrace south of ScottsCreek (Photo 8) and inland along Swanton Road. Based onsite visits and first-hand visual observations near the mouthof Scotts Creek (37.0413 N, −122.2277 W) by the author in2013, there appeared to be abundant (regrowth of) shrub andwoodland cover in the marshland area.

Other locations of change on the coast

Several other locations in the coast region shown in Fig. 1were examined with imagery and visited by the author forfirst-hand observations of vegetation. Detailed figures werenot included for the site narratives that follow.

Devil’s Slide (37.5745 N, −122.5180 W): The coast high-way (CA Route 1) between Pacifica and Montara has a longhistory of closure due to rockslides and land slippage, and is

aptly named the Devil’s Slide area. The Devil’s Slide Tun-nels Project was initiated in 2005 for the construction of two

Fig. 5 Overlay of LEDAPSresults for the Ano Nuevo StateReserve area (Point IV in Fig. 1)onto NLCD land cover types

Photo 7 View along the Cascade Creek Trail in AnoNuevo State Reserve

C. Potter

tunnels beneath San Pedro Mountain. LEDAPS results forthe area showed a band of lost perennial vegetation cover300 m wide (west to east), starting at points about 750 m east(inland) of the Tunnels Project site. Due to the steep rockycliffs on Devil’s Slide, no changes in vegetation cover at theactual Tunnels Project site were detected between 1999 and2009.

Pigeon Point (37.1825 N, −122.3938 W): Restorationprojects at the Light Station State Historic Park have beenundertaken by the California State Parks. LEDAPS resultsfor scrub-dominated plant communities on the coastal ter-races surrounding Pigeon Point showed extensive increase inevergreen vegetation cover between 1999 and 2009.

Gazos Creek Beach (37.1627 N, −122.3606 W):Franklin Point (Fig. 5) is the southern extent of GazosBeach, which serves as a protected haul-out area for marinemammals. LEDAPS results for the beach area just westof CA Route 1 showed nearly 5 ha of lost perennial vege-tation cover between 1999 and 2009. Many exposed sanddunes were observed in this same beach area in 2013,suggesting recent erosion events, the exact causes of whichwere unknown.

Wilder Ranch (36.9830 N, −122.0905 W): Agriculture ispracticed year-round on 600 leased acres (240 ha) of

parkland between CA Route 1 and the Pacific Ocean. ThisState Park is also notable because it encloses two other

Fig. 6 Overlay of LEDAPSresults for the DavenportLanding area (Point V in Fig. 1)onto NLCD land cover types

Photo 8 Coastal terrace south of Scotts Creek near Davenport Landing

Land cover change on the California coast

properties: the Santa Cruz City Landfill and Granite RockSand Quarry. LEDAPS results for plant communities alongWilder Creek, Needle Rock Point, and Wilder Beach allshowed increases in evergreen vegetation cover between1999 and 2009. The only notable loss of evergreen vegeta-tion cover was detected boarding the Moore Creek drainage,adjacent to the University of California Santa Cruz maincampus (36.9821 N, −122.0679 W).

Conclusions

The LEDAPS methodology has proven to be effective formapping vegetation disturbance and regrowth patternsacross much of North America (Masek et al. 2008). Thepotential for changing climate along the California coast(i.e., increase in surface temperatures and declines in fogextent; Johnstone and Dawson 2010) and sea level rive(Hanak and Moreno 2012) makes the monitoring of suchvegetation responses more urgent than ever for the region.The LEDAPS methodology can fulfill much of the need forcontinual, low-cost monitoring of emerging damage to coast-al habitats, especially for locations where rare and endan-gered species have been documented.

Documentation of vegetation restoration for positive en-vironmental and recreational impacts over the past decadewas demonstrated by the LEDAPS methodology for exem-plary locations such as Pillar Point, Ano Nuevo State Re-serve, and Scotts Creek Marsh. The advantages of routine,large-scale Landsat mapping of changes in perennial veg-etation cover (as opposed to occasional ground surveys)includes the benefit that LEDAPS results are not depen-dent on repeat cover type mapping, such as the effortundertaken for the NLCD. Once the proper thresholdsfor ΔDI values have been determined for a given re-gion, it is possible to compute the highest probable areasof ecosystem disturbance or vegetation regrowth/restora-tion every year for which cloud-free Landsat imagery isavailable.

Acknowledgements This work was supported by grants from NASAAmes Research. The author thanks Tim Hyland, Environmental Scien-tist, California State Parks for assistance with image interpretations andhistorical information on the Ano Nuevo State Reserve area.

References

California Beach Erosion Assessment Survey (CBEAS) (2010) Califor-nia Coastal Sediment Management Workgroup, Sacramento, CA

California Coastal Conservancy (2004) Pillar point bluff acquisitionand trail planning, Staff recommendation, June 30, 2004, File No.04–026, 8 pp

Cohen WB, Goward SN (2004) Landsat’s role in ecological applica-tions of remote sensing. BioScience 54:535–545

Crist EP, Cicone RC (1984) Application of the tasseled-cap concept tosimulated thematic mapper data. Photogramm Eng Remote Sens50:343–352

Curry R, Houghton R, Kidwell T, Tang P (1985) Pescadero marsh man-agement: A plan for persistence and productivity. January 28:1985

Environmental Science Associates (ESA) (2008) Pescadero marsh:Restoration assessment and recommendations for ecosystem man-agement. Prepared for the California Department of Parks andRecreation, San Francisco, p 54

Hanak E, Moreno G (2012) California coastal management with achanging climate. Clim Chang 111(1):45–73

Healey SP, Cohen WB, Zhiqiang Y, Krankina ON (2005) Comparisonof tasseled-cap-based Landsat data structures for use in forestdisturbance detection. Remote Sens Environ 97:301–310

Huang C, Wylie B, Yang L, Homer C, Zylstra G (2002) Derivation of atasseled-cap transformation based on Landsat-7 at-satellite reflec-tance. Int J Remote Sens 23:1741–1748

Johnstone JA, Dawson TE (2010) Climatic context and ecologicalimplications of summer fog decline in the coast redwood region.Proc Natl Acad Sci. doi:10.1073/pnas.0915062107

Kauth RJ, Thomas GS (1976) The tasseled-cap—A graphic descriptionof the spectral–temporal development of agricultural crops as seenby Landsat. Proceedings, Symposium on Machine Processing ofRemotely Sensed Data. LARS, West Lafayette, pp 41–51

Kildow J, Colgan CS (2005) California’s Ocean Economy, Report tothe Resource Agency, State of California, National Ocean Eco-nomics Program, July 2005

Masek JG, Huang CQ, Wolfe R, Cohen W, Hall F, Kutler J, Nelson P(2008) North American forest disturbance mapped from a decadalLandsat record. Remote Sens Environ. doi:10.1016/j.rse.2008.02.010

Rahmstorf S (2007) A semi-empirical approach to projecting future sea-level rise. Science 315:368–370

C. Potter