monitoring loggerhead sea turtle ( caretta caretta ) nests in turkey...

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Monitoring Loggerhead SeaTurtle (Caretta caretta) Nestsin Turkey Using GISDerya Maktav, Filiz Sunar, Denizhan Yalin, ErsoyAslanPublished online: 29 Oct 2010.

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Coastal Management, 28:123–132, 2000Copyright ã 2000 Taylor & Francis0892-0753/00 $12.00 + .00

Monitoring Loggerhead Sea Turtle (Caretta caretta)Nests in Turkey Using GIS

DERYA MAKTAVFILIZ SUNARDepartment of Remote SensingIstanbul Technical UniversityMaslak, Istanbul, Turkey

DENIZHAN YALINDepartment of SurveyingIstanbul Technical UniversityMaslak, Istanbul, Turkey

ERSOY ASLANDepartment of GeodesyIstanbul Technical UniversityMaslak, Istanbul, Turkey

Both the loggerhead sea turtle (Caretta caretta) and the green turtle (Chelonia mydas)live, feed, and nest in the Mediterranean, mostly on the beaches of Turkey andGreece. The greatest threat to the survival of Caretta caretta has been found to be onthe sandy beaches where their lives begin. In this study, the digital terrain model(DTM) of the Iztuzu Beach in Turkey where the Caretta caretta sea turtles lay theireggs was prepared using a global positioning system (GPS) and a geographic infor-mation system (GIS). A flexible coastal geographic information system was preparedintegrating the DTM with digitally processed satellite images and ground truthof the nesting area and its surroundings. Researchers, decision makers, other endusers, or sea turtle experts can find and query any environmental information hav-ing a possible impact on the nesting area using a computer-based GIS database. Amultidate monitoring of the nesting area allows users to extract and compare muchinformation about the location and condition of the nests and will help researchersdevelop better strategies for protecting sea turtles.

Keywords coastal geographic information system, global positioning system, satel-lite imagery, sea turtle

Received 16 September 1998; accepted 30 May 1999.Grateful acknowledgment is made to the European Space Agency (ESA), the Istanbul Tech-

nical University Research Fund, and SPOT Image for the support of the International Mediterra-nean Project (IMP). Thanks are expressed to the FORD, World Heritage, and Council of Europefor deeming the IMP worthy of the Henry Ford European Conservation Awards 1998 NationalAward.

Address correspondence to Prof. Dr. Derya Maktav, Faculty of Civil Engineering, Depart-ment of Remote Sensing, Tstanbul Technical University, 80626, Maslak, Istanbul, Turkey.E-mail: [email protected]

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124 D. Maktav et al.

The sea turtle has been living on our planet for millions of years. They are 110 to 140cm large, air-breathing reptiles that inhabit tropical and subtropical seas throughout theworld and weigh up to 200 kilograms (Sielmann, 1982). It is theorized that some spe-cies can live over 100 years. Scientists recognize eight living species of sea turtle (caretta,mydas, agassizi, imbricata, kempii, olivaceaf, depressus, and coriacea) which are groupedinto six genera. Two species of sea turtle nest along the Mediterranean shores of Tur-key, namely, the loggerhead turtle (Caretta caretta) and the green turtle (Chelonia mydas).Caretta caretta has a worldwide distribution, with the population estimated to be be-tween 100,000 and 200,000 adults (Erkakan, 1993; Groombridge, 1988). Both speciesare highly endangered in the Mediterranean mainly due to human pressures and the lossof their nesting habitats (Kasparek, 1991, 1993; Venizelos, 1995; Whitmore, Jesu, &Reynolds, 1991). Substantial nesting of the Caretta caretta now occurs at fewer than 20beaches in Turkey and Greece. The 2500 km of Turkish Aegean and Mediterraneancoastline was completely surveyed in 1988 and 17 major nesting beaches were found(Bentivegna & Paglialango, 1997; Erkakan, 1993; Geldiay, 1982; Venizelos, 1989, 1990,1991; World Wide Fund (WWF), 1989). All known nesting sites of both species arefacing an increasing threat from anthropogenic developments, such as tourist develop-ment, marine pollution, sand and shingle extraction, incidental catch by fishermen, mari-time traffic, etc., and as a result the number of nesting turtles (females) has decreasedsharply (WWF, 1989). Therefore, any nesting site of sea turtles in the Mediterraneanneeds protection, and urgent action needs to be taken to counteract these threats.

General recommendations to counteract threats such as tourist development, marinepollution, sand and shingle extraction, incidental catch by fishermen, and maritime traf-fic include planning a complex coastal zone management plan for the Turkish Aegeanand Mediterranean regions, establishing a network of nature reserves along the coast toprotect the 17 particularly important sea turtle nesting beaches, and initiating a programfor seasonal or yearly long-term monitoring of sea turtle populations and threats to theirsurvival (WWF, 1989).

Before preparing and subsequently applying the coastal zone management plansmentioned above, computer-based coastal geographic information systems are needed.With large amounts of digitized data from many different sources, such as land-basedinformation (land use cover, digital terrain model [DTM], nesting location, etc.), datacollected from the water side of the coast (water pollution, nearshore currents, gradients,bottom materials, etc.), information about the sea/land interaction (such as beach erosion),and meteorological data, these systems make it quick, cost-effective, and much easier toprepare the needed coastal management plans. A pilot project called the InternationalMediterranean Project (IMP), coordinated by the Istanbul Technical University, has beendeveloped in Turkey with the aim of preparing such a coastal geographic informationsystem (GIS) in a pilot study area at the Köycegiz-Dalyan specially protected area alongthe Turkish Mediterranean coast (Maktav & Kapdasli, 1996). The inputs of this systemwhich fulfill these requirements were obtained from the following resources:

· raster data: optical (LANDSAT-Thematic Mapper, SPOT-Panchromatic, and KFA-1000)and radar (ERS-SAR) satellite data;

· vector data: digitized land use plans and topographical maps, bathymetric map of thelake, the DTM of the nesting beach (Maktav & Kapdasli, 1996);

· ancillary (tabular) data: meteorological (mean temperature, mean and max wind velocityand its direction, mean relative humidity), census (population growth and distribution),hydrological (precipitation, flow, evaporation, drainage area, rainfall runoff model, flood),oceanographic (salinity, water temperature, specific conductivity, dissolved oxygen, re-dox, pH values, and turbidity in 2-m intervals), and agricultural (cadastral number foreach field, location, area, area cultivated with each crop, year of last cultivation, particlesize distribution).

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Monitoring Loggerhead Sea Turtle Nests Using GIS 125

Many simple methods are used for investigating sea turtle survival including: count-ing the total number of nests and the number of nests successful in producing hatchlingsthat reached the sea; counting the numbers of female adults, total eggs, damaged ordecayed eggs; and measuring nest depths using simple tapes. However, researchers needto know many other characteristics to develop contemporary strategies for protecting seaturtles such as migration paths, precise locations of nests (nest temperature, determina-tion of sex ratio, overwash, etc.), and the length of time baby turtles spend in the opensea. Furthermore, examining the nesting sites alone is insufficient. Any anthropogenicdevelopments or ecological and environmental changes over time related to the sur-roundings which could affect the nesting area should be investigated carefully. Withthese more difficult and complex characteristics, new technologies such as space-bornetechnologies (satellite remote sensing, global positioning systems [GPSs]) and GIS canbe very useful. For example, satellite telemetry (radio signals) using NOAA satellites isallowing researchers to monitor sea turtles throughout their range of migration. Theinformation gathered through satellite tracking should answer many questions and helpconservation groups develop better strategies for protecting sea turtles. For example, thetracking results obtained in October 1995 showed that most Caretta carettas found inthe mid-southern to southern regions of the Tyrennian Sea come from the eastern basinof the Mediterranean Sea (Bentivegna & Paglialango, 1997).

This article examines the use and applicability of GPS, GIS, and satellite remotesensing technologies for monitoring the precise locations of sea turtle nests, for collect-ing and analyzing environmental (here, mainly land- and lake-based) information intheir surrounding areas, and for determining possible environmental impacts on thesenests on a Mediterranean beach in Turkey to develop management plans for protectionof the sea turtles.

Study Area

Dalyan-Iztuzu Beach is part of a specially protected area declared by the Turkish gov-ernment, and is approximately 4.2 kilometers long and includes two beaches to the west,Dalyanadzi Ekincik (Figure 1). The approximate geographic coordinates of the studyarea are 28º35’E, 37º00’N (upper left) to 28º50’E, 37º20’N (bottom right). The number ofnests for this combined beach complex is between 235 and 255 nests per year. The peaknesting period is the middle of June, and the eggs incubate for about 60 days (Erkakan,1993; Poland, 1996). When our survey team visited the Iztuzu Beach in August 1997,we recognized 65 sea turtle nests with hatchlings. We surveyed the nesting area usingGPS measurements to fix the nest locations and prepared a DTM on August 28–31,1997, when the hatchlings were emerging from their nests.

Material and Methods

GPS is a worldwide radio-navigation system formed from a constellation of 24 satellitesplaced in orbits at about 20,000 km altitude above the earth’s surface and their groundstations, which allows measurements to better than a centimeter. The final arrangementof satellites is planned in such a way that at least four satellites are simultaneouslyvisible above the horizon anywhere on earth, 24 hours a day. The whole idea behind itis to use satellites in space as reference points for locations on earth. To precisely deter-mine the locations of the 65 sea turtle nests along the Dalyan-Iztuzu shores, a GPSnetwork in the vicinity of the province Mugla was established. The geocentric (earth-centered) coordinates of the network points measured in the World Geodetic System1984 (WGS-84 mathematical ellipsoid (geoid) satellite system) were transformed into

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Figure 1. Dalyan-Iztuzu and Ekincik Beaches.

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the Universal Transverse Mercator (UTM) coordinate system in Turkey using knowntransformation parameters. Leica SR399 dual frequency GPS receivers for identifyingthe positions of the network have been used.

In the combined beach complex there is a line of 316 numbered, wooden postssunk into the sand which run the entire length of the beaches at regular intervals of 5and 10 m (306 posts in our study area “Dalyan-Iztuzu Beach”). The line is approxi-mately 25 m from the southern coastline. The fixed posts are used for researchers toperiodically measure the positions of nests with hatchlings, and also to prevent touristsfrom sunbathing in the area and damaging nests. The coordinates of the fixed woodenposts and all of the known nests were also measured with GPS using a static positioningmethod with a stationary receiver mounted in the Köycegiz small harbor, connected tothe local network and transformed to the UTM coordinate system. Some control mea-surements were also made using Wild 1600 electronic tacheometry.

The DTM with 25-cm contour intervals of the Dalyan-Iztuzu Beach where the Carettacaretta nests are located was prepared using GPS data (see Figure 2). The contours ofthe sandy terrain are between 0 and 4 m above sea level. Using the digital model inArcView-GIS software, one can extract the information that all nests are located onlybetween the contours of 0.50 and 1.25 m (Figure 2, small points along the sea shore onthe zoomed part). Although the sand is flat in many parts of the northern region of thebeach along the wetland shores beach, no nests are located there.

A GIS is a database system for manipulating digital spatial and thematic data and isan important tool for environmental monitoring and management (Krishnan, 1997). Inthe pilot project, ArcView-GIS Version 3.0, a software for visualizing, exploring, query-ing, summarizing, organizing, and analyzing different geographic data is used. Itsupports analytical tools that create spatial data and define spatial relationships amongmultiple sets of disparate data stored in its relational database (Environmental SystemsResearch Institute [ESRI], 1995). The pilot coastal GIS we prepared comprises raw (zoomedpixels) and digitally classified (classes being forests, water-covered areas, shallow water,vegetation, settlement areas) satellite images and the above-mentioned ground truth fromthe specially protected area including the Iztuzu Beach (Figure 3). The DTM of theIztuzu Beach including the southern coastline in ArcView-GIS is merged with registeredERS-1/2, LANDSAT-TM, SPOT-P, and KFA-1000 satellite images and all other ancil-lary ground truth data. Also positions of the above-mentioned wooden posts and nestsusing transformed UTM coordinates were transferred into the ArcView-GIS layers (Fig-ure 3). Thus, all data are merged into one information system so that researchers orother end users can monitor, explore, analyze, and query data to determine possibleimpacts on the overall survival of the sea turtle choosing any of the different data setsused. A good example of utilizing satellite imagery to protect the sea turtles is thedigital classification of LANDSAT-TM data to obtain information about water pollutionalong the Iztuzu coasts (Maktav & Kapdasli, 1995). Comparing the classification resultsof the classified multidate satellite images for water pollution and nesting conditionssimultaneously, it is very easy to evaluate the negative or positive impacts of the in-creased or decreased water pollution on sea turtle survival.

Results and Discussion

The main factors directly effecting sea turtle nests are water pollution (Maktav & Kapdasli,1995), coastal erosion (Maktav & Kapdasli, 1996), population growth, tourism and re-lated coastal structures, damage of coastal topography, and coastline morphology (Maktav& Kapdasli, 1995). Considering that the coastal areas are very large and of differentgeographical positions and are even sometimes not accessible, raw/classified and regis-

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Figure 2. Contour intervals of the Dalyan-Iztuzu Beach where the Caretta caretta nests arelocated using GPS data.

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Figure 3. Satellite images of specially protected area of Iztuzu Beach.

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tered satellite images with their synoptic views will be very useful, cost-effective toolsfor monitoring, determining, and evaluating these factors as a whole. Today the highestspatial digital resolution obtained by the commercial earth monitoring satellites is ap-proximately 10 × 10 m. Although satisfactory for monitoring and evaluating environ-mental factors affecting their survival, this resolution proves insufficient when trying tomonitor the sea turtles directly. However, in 1999 the satellite “Quickbird” will allow apanchromatic resolution of less than 1 m, which will probably enable us to recognizethe sea turtles or turtle groups directly in the scene. These imageries probably will givemuch better and accurate results in the near future for wildlife monitoring.

GIS simplifies computation of sea turtle nest positions, requiring easy manipulationof a cursor. For example, using GIS to graphically visualize and analyze the data, it wasclear that the 65 nest distances from the southern coastline varied between 10 and 30 m,and showed that not even one sea turtle went beyond 30 m from the coastline to laytheir eggs regardless of whether the terrain sloped or was flat. Using the digital model inArcView-GIS software, one can also extract the information that all sea turtle nests arelocated only between the contours of 0.50 and 1.25 m.

Another advantage of GIS is that all satellite data and land/water-based ground truthmentioned above can be combined in one system as a whole. Having this kind of aunique information system, one can easily extract any information, such as the precisepositions of the nests and the distances between them. Impact of land use or population/tourism developments on sea turtles interpreted using digitally classified satellite imag-eries can be queried using GIS.

Considering that all data in GIS are of different dates, the computer-based GISenables quick and easy determination and evaluation of the multitemporal changes, bothqualitatively and quantitatively. For example, using separate layers to show the numberof different nest groups on different dates, it is easy to correlate these with variousenvironmental, ecological, and land use changes (obtained using satellite data and changedetection analysis methods). In this way many improvements can be made in developingstrategies to further sea turtle survival.

In Turkey there are 17 Caretta caretta nesting areas at the Aegean and Mediterra-nean coasts. The most reliable method to monitor all these nests in different nestingperiods and to combine them all in one system is the integrated use of GPS and GIS.This can also be done on an international basis. Advanced forms of GPS have a posi-tioning precision of less than a centimeter. This makes precise and quick determinationof Caretta caretta nest locations on digital maps within the GIS possible.

Satellite technologies and GIS would be valuable tools for monitoring and investi-gating sea turtle survival. However, it is essential to do this work periodically in conve-nient (nesting) seasons. After that, comprehensive national and even international coastalzone management plans are necessary to ensure that the conservation requirements ofsea turtles (and other wildlife) are fully integrated into, and not damaged by the devel-opment of, tourism and other activities.

The main goal of this article is to show the applicability of GPS technology to themonitoring of the locations of the sea turtle nests, the useability of the integration of thesatellite data and GPS with ground truth in determining the environmental impacts onthe sea turtle nests, and the combination and evaluation of all this data in a GIS.

Considering this specific goal, the expenses are relevant for purchasing satellitedata, for processing of this data and purchasing related hardware and software, for pur-chasing GPS and GIS hardware and software, and for fieldwork and office work ex-penses. The costs (except software and hardware, if no upgrades are needed) will beincreasing with increasing numbers of periodical measurements. For investigating a smallmonitoring area, say 1 km, with a small number of sea turtle nests only, use of satellite

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data and GIS perhaps would not be very cost effective. However, with a nesting area of5 to 10 km or longer, which is generally the case, use of satellite data, GPS, and GISwill be very cost effective in determining and evaluating the environmental impacts. Togive a concrete example, monitoring water pollution in a large surrounding area withconventional environmental techniques needs much personnel, time, and money. How-ever, in this case, calibration of digitally processed satellite data even with a few mea-surements done on some selected water stations only will enable us to obtain satisfac-tory information about water pollution in the whole water-covered area which couldhave negative impacts on sea turtle survival. This will, of course, decrease the researchcosts greatly.

In this study, though financial and time constraints prevented us from monitoringnest locations during different nesting periods (and subsequently tracking the multidatenesting paths), it was seen that even a limited single-season survey using space-basedmonitoring methods and a GIS could significantly help researchers and conservationgroups investigating sea turtle survival. Future improvements will include the use of anyadditional periodical data for improving the effectiveness of the system established.

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monitoring loggerhead sea turtle ( caretta caretta ) nests in turkey...

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