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THE ABANDONMENT OF OLIVE GROVES IN THE AEGEAN ISLANDS, GREECE: CAN A SOCIO-ECONOMIC PROBLEM BECOME AN ECOLOGICAL ASSET? By N.S. MARGARIS 1 and M. THEODORAKAKIS 2 Abstract: Olive plantations have been cultivated in the Aegean Islands of Greece for many centuries. However, intensive cultivation of seed oils has nowadays dominated and new products such as soya oil, maize oil and sunflower oil have become available on the market as substitutes for olive oil. For this and other social and customary reasons, cultivation of olive groves was, therefore, abandoned in many of the Aegean Islands. In the present paper the environmental importance of abandoned olive groves as typical Mediterranean ecosystems was studied and the importance of biological diversity in these olive groves was confirmed. It is therefore suggested that olive groves must be protected even if the product is no longer collected. Key words: Olive, Olea europaea, Greek islands, Mediterranean cultivation, Olive groves, abandonment Introduction The isolation of the Aegean Islands and the scarcity of resources forced their people to develop three special systems of agriculture: wet season cereals, vineyards and olive groves. These systems were in place almost throughout the Mediterranean basin and were interlocked between each other during many centuries of human activity. Wet season cereals (wheat and barley) planted after autumn rains demand a great deal of effort from the farmers to collect, threshing and processing from June through July until the middle of August. After this period, the collection of grapes starts. The collection ends in October, followed by the collection of olives. Great changes have occurred during the last few decades within the primary sector affecting almost all parameters related to the cultivation of traditional Mediterranean products. These changes are connected with advances in: mechanization, such as the introduction of tractors and harvesting machines genetics, such as new varieties and hybrids 1 Division of Terrestrial Ecosystems, Dpt of Environmental Studies, University of the Aegean 2 Annex of Forestry, Technological Educational Institute (T.E.I.) of Lamia 1

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THE ABANDONMENT OF OLIVE GROVES IN THE AEGEAN ISLANDS, GREECE: CAN A SOCIO-ECONOMIC PROBLEM BECOME AN ECOLOGICAL ASSET?

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THE ABANDONMENT OF OLIVE GROVES IN THE AEGEAN ISLANDS, GREECE: CAN A SOCIO-ECONOMIC PROBLEM BECOME AN

ECOLOGICAL ASSET?

By N.S. MARGARIS1 and M. THEODORAKAKIS2

Abstract: Olive plantations have been cultivated in the Aegean Islands of Greece for many centuries. However, intensive cultivation of seed oils has nowadays dominated and new products such as soya oil, maize oil and sunflower oil have become available on the market as substitutes for olive oil. For this and other social and customary reasons, cultivation of olive groves was, therefore, abandoned in many of the Aegean Islands. In the present paper the environmental importance of abandoned olive groves as typical Mediterranean ecosystems was studied and the importance of biological diversity in these olive groves was confirmed. It is therefore suggested that olive groves must be protected even if the product is no longer collected.

Key words: Olive, Olea europaea, Greek islands, Mediterranean cultivation, Olive groves, abandonment

Introduction

The isolation of the Aegean Islands and the scarcity of resources forced their people to develop three special systems of agriculture: wet season cereals, vineyards and olive groves. These systems were in place almost throughout the Mediterranean basin and were interlocked between each other during many centuries of human activity. Wet season cereals (wheat and barley) planted after autumn rains demand a great deal of effort from the farmers to collect, threshing and processing from June through July until the middle of August. After this period, the collection of grapes starts. The collection ends in October, followed by the collection of olives.

Great changes have occurred during the last few decades within the primary sector affecting almost all parameters related to the cultivation of traditional Mediterranean products. These changes are connected with advances in: mechanization, such as the introduction of tractors and harvesting machines genetics, such as new varieties and hybrids chemistry use of fertilizers and pesticides the high cost of transporting agricultural products food technology, such as refrigerators, pasteurized juices, frozen products and improvement in irrigation technology (Margaris, 1992).However, it has been impossible to apply mechanization to the olive groves, up to

the stage of collection, since no new method has been developed. In addition extensive agriculture has nowadays come to be dominated by intensive methods of cultivation.

Since it has been impossible to mechanize olive cultivation, specially in the islands where the flat land was kept for the annual crops and the most olive groves were small family ownerships growing on marginal places, or steep slopes with difficulty in approach, (Anthopoulou, 1993), substitutes for the basic product, olive oil, have recently appeared on the Mediterranean market. During the last twenty years in Greece, the oil coming from annual intensive agriculture either directly (sunflower, maize oil) or indirectly (cotton oil) has taken a real share of the market, and year by year consumers are turning to these new products.

1 Division of Terrestrial Ecosystems, Dpt of Environmental Studies, University of the Aegean2 Annex of Forestry, Technological Educational Institute (T.E.I.) of Lamia

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As a consequence, the share of seed oil in the Greek oil market has increased within six years from 20% in 1983 to 36% in 1989. A similar trend was observed in Italy, where the seed oil share in the market increased from 41% to 49% within ten years (1979-1989), decreasing that of olive oil from 44% to 33% during the same period. Oil prices have played an important role in the substitution of olive oil by seed oils. The ratio of the prices of sunflower oil over olive oil 1:1.37 in 1985 was increased to 1:1.73 in 1985 and finally climbed up to 1:4.0 in 1991.

The result of the decline in demand for olive oil is that olive plantations have been abandoned. But this was not the only reason.

Olive groves in the islands

From the 1,722,500 acres of olive groves in Greece, 660,000 (38.3%) are located in the islands.

One problem of olive cultivation, which becomes even more intense in the islands, is fragmentation. Mainly for reasons of inheritance, but also of dowry, the large olive groves are fragmented again and again as they go down from father to son. The result of this practice is the current situation. Throughout Greece, 61.22% of olive groves are no bigger than 7.5 acres (Therios, 1985). This percentage grows even more if calculated only for the island olive groves, because it is precisely in the islands that properties are mainly owned by families, which means that they can be divided by the owner, not being owned by any cooperation. The properties are divided even more as the family expands. The sons and daughters that grow up and create new families take their own shares of the family olive grove. Of course, if later on the new family is swept by the tide of urbanization and moves to the city, the small and unprofitable –as far as the cultivation is concerned– olive grove is usually abandoned.

In the islands, where lowlands are scarce and, if present, are used for annual cultivations (mainly grain), olive groves have inevitably found refuge on hillsides or difficult to access, semi-mountainous plateaus. Olive cultivation in the islands and the mainland is significantly different. For example, in Lesbos there is a wide range of olive groves of every type and in various degrees of abandonment. The remote sensing methods that we used in Lesbos recorded 18,572 acres (19%) of good productivity olive groves, 39,322 acres (40.3%) of medium productivity, 19,682 acres (20.2%) ruined due to frost or other factors, 2,285 acres (2.3%) of long-term abandonment and 17,618 acres (18%) of recent abandonment. The total comes up to 97,479 acres of olive groves, 20.000 acres of which have been abandoned (satellite image, 1990). It is a percentage of 20% on an island where olive cultivation is supposed to be flourishing. What kind of percentages would we find in other islands? In the present work a comparative study was carried out on the diversity of the flora and fauna of cultivated and abandoned olive groves.

Environmental importance of olive groves

Olive tree and the community it forms, the olive grove, is a unique and inseparable element of landscape in the Mediterranean basin. However, its ecological significance and value has been, if not completely, partially, overlooked. Many ecologists consider the olive grove as a type of cultivation that is interesting only from the agricultural point of view for its economic significance. However, the cultivated olive grove is a special kind of agro-ecosystem with certain characteristic features. It certainly differs

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from other relevant agro-ecosystems that are from other trees’ cultivations, with regard to the following: The olive grove continues to be productive to a certain extent with the minimum of cultivation and care. It can survive under very adverse conditions such as lack of water and nutrients, on poor and shallow soils, etc. After its abandonment it has the potential to evolve to a Mediterranean type ecosystem, even in marginal conditions such as steep slopes. After years of total abandonment it can recover and revert to its initial state under appropriate cultivation techniques; although this is very difficult or even impossible for other types of tree cultivation.The floristic components of olive groves classified by biotic type revealed high

similarity between olive groves and Greek Mediterranean-type ecosystems (table .1.).

Table .1. Percentage composition of biotic types in olive groves and in natural ecosystems.[1. Authors mentioned by Vokou (1988), 2. This research, 3. Low altitude (0-600  m.) natural ecosystem, Mount Kyllini, (Dimopoulos, 1993), 4. Mediterranean type Greek ecosystems (Vokou, 1988)]

BIOTIC TYPE 1 2 3 4(%) (%) (%) (%)

Therophyta 52 52 39 45Geophyta 16 4 12 12Hemi-cryptophyta 23 24 31 25Chamephyta 3 8 5 7Phanerophyta 6 13 13 8

It is evident that the artificial "olive grove" ecosystem, in contrast to what is happening in other agro-ecosystems, is much closer to the natural Mediterranean ecosystem (Margaris, 1981), even in its functional-productive phase (i.e. when not abandoned).

This contrast may be attributed to the following factors: The cultivated olive tree (Olea europaea var.europaea L.) and the wild olive

tree (O. europaea var. sylvestris Brot.) are the same species. The type of traditional olive grove management in Greece. The fact that the wild olive is a characteristic species of the Oleo-Ceratonion

vegetation zone.

Biological diversity of olive groves

Olive groves seem to be positively related to other environmental resources, which are the quality of soil and the existence of plant and animal species. Data showing plant species in olive groves are given in table 2.

Data concerning the presence of birds in olive groves of the Aegean Islands of Lesvos, Chios and Skyros are presented in table 3.

These ornithological data are of special interest according to Bird Life International, who has supported the view that the results of phase (I) of the project (Conservation of Dispersed Species in Europe) have shown that second to wetland birds, birds of agricultural habitats are generally the most threatened in Europe. (G.M. Tucker, personal communication).

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Another group in the fauna of olive groves of high interest is the insects. Since the insect-plant interaction is well established, it is also expected that the presence of insects in the olive grove is dependent on the vegetation. Species number, size of individual populations and their distribution inside a specific olive grove, are dependent on many factors, the most important of which are:

Plant diversity and the level of vegetation development. The age of the olive grove. The length of the period since abandonment. The presence or absence of grazing animals. The vegetation parameters of the surrounding area. The recent climatic conditions (e.g. a very dry summer period). The extent of the impact of the human activities on the area (e.g. spraying

with pesticides). Data concerning the presence of insects in olive groves of the Aegean Islands of

Skyros and Lesvos are presented in table 4 and 5.

Table 2: Flora of olive groves and number of plant species in each family. Column numbers are referring to authors: 1. Pavlidis (1976), 2. Christodoulakis (1986), 3. Economidou (1969), 4. Turrill (1929), 5. Rauh (1949), 6. Charistos (1968), 7:This research (1993)

No Families 1 2 3 4 5 6 7Pteridophyta - - - 5 - - -

1 Amaranthaceae - - - - - - 12 Anacardiaceae - - 1 - - - 23 Araceae - - 1 3 2 - -4 Boraginaceae - - 3 - - - 35 Campanulaceae - 1 - - - - -6 Capparidaceae - - - - - - 17 Caryophyllaceae - 2 1 1 1 - 38 Caprifoliaceae - - - - - - 19 Chenopodiaceae - - - - - - 210 Cistaceae 1 - 3 - - - 311 Compositae 8 8 22 4 7 1 3112 Convolvulaceae - 1 - - - - 213 Cruciferae - - 4 - 5 - 714 Cynocrambaceae - - - - -1 -15 Dioscoraceae - - 1 - - - 116 Dipsacaceae - - - - 2 - 117 Ericaceae - - 1 - - - -18 Ephedraceae - - - - - - 119 Euphorbiaceae - 1 2 - 3 - 620 Fagaceae - - 1 - - - 121 Gentianaceae 2 - 2 - - - 322 Geraniaceae 1 - 1 - - - 523 Graminae - 2 14 8 2 - 2324 Guttiferae 3 2 2 - 1 - 125 Iridaceae 1 - 2 1 - - -26 Labiatae 1 - 8 4 3 - 1827 Leguminosae 15 1 28 2 7 - 3328 Liliaceae 1 - 5 1 6 - 429 Linaceae 2 1 3 - 1 - 330 Malvaceae - 1 - - 1 - 231 Oleaceae 1* 1* 1* 1* 1* 1* 3

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32 Orchidaceae 10 - 4 1 1 - 133 Orobanchaceae - - 2 - - - 234 Oxalidaceae - - - - 1 - -35 Papaveraceae - 1 3 - 3 - 336 Plantaginaceae 1 - 3 - - - 437 Polygonaceae - - 1 - - - 238 Primulaceae - - - - - - 239 Rafflesiaceae - - - - - - 140 Ranunculaceae 1 2 3 2 1 1 241 Resedaceae - - 1 - - - -42 Rhamnaceae - 1 - - - - -43 Rosaceae - 1 4 - - - 444 Rubiaceae 2 - 3 - 1 - 545 Santalaceae - - - - - - 146 Scrophulariaceae 1 2 5 5 1 - 547 Simaroubaceae - - - - - - 148 Solanaceae - - - - - - 149 Umbelliferae 3 2 6 3 9 - 950 Urticaceae - - - - - - 451 Valerianaceae - - 2 - - - -

TOTAL 54 30 143 41 60 3 207* Olea europaea is being added to all authors.

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Table .3. Observed bird species in the olive groves

Column 1 :Lesvos Isl., Column 2 : Chios Isl., Column 3 : Skyros Isl. Column 4 : Abandonment status of the olive grove in which the species observed MA= Abandoned for many years (>10), A= Abandoned, C= Cultivated. -= Not observed inside the olive grove or the species is not showing any particular preference to the previous categories. Column 5 : Month of appearance (e.g. 3-5 observed from March to May, 3/5 observed March and May). Column 6 : Frequency of presence inside the olive grove (Scale 0-4). 0= extremely rare, 1= Rare, 2 Relatively rare,3= Common, 4= Very common. Column 7 : Plant cover percentage of the olive grove in which the species is most commonly observed. (- =No correlation between the plant cover and the presence of the observed species)

No Species 1 2 3 4 5 6 71. Acanthis cannabina + + MA 5 2 602. Accipiter gentilis + - 3/9 2 -3. Accipiter nisus + + - 9-10 2 -4. Alauda arvensis + + + A 5 1 <405. Alectoris chucar + + MA 4/10 2 406. Anthus trivialis + + + A/C 5/9-10 3 <407. Anthus campestris + A/C 6 1 508. Anthus pratensis + + + A/C 11-1 3 <409. Apus apus + + + - 5-9 3 -10. Apus melba + + + - 5-9 2 -11. Apus pallidus + + - 5-9 2 -12. Asio otus + + A 11 1 5013. Athene noctua + + + C/A - 3 40-5014. Bubo bubo + + MA 10 1 5015. Buteo rufinus + - 9 1 -16. Buteo buteo + + + - 9-11 2 -17. Calandrella brachydactyla + + A/C 4-5 3 <3018. Caprimulgus europaeus + + C/A 6/9 2 -19. Carduelis cannabina + + MA/A - 3 -20. Carduelis carduelis + + + A - 3 -21. Carduelis chloris + + + C/A 4-5/10 3 -22. Certhia brachydactyla + C/A 5 2 -23. Cercotrichas galactotes + + MA 6 2 >6024. Circaetus gallicus + - 9 1 -25. Coccothraustes coccothraustes + + MA/A 10-2 2 6026. Columba palumbus + + A 1-2 4 5027. Corvus corone corone + + MA/A 5/9 2 -28. Corvus corone cornix + + + - - 4 -29. Crex crex + + MA 10 1 >6030. Cuculus canorus + + + C 4-5 3 50-6031. Delichon urbica + + + - 5-9 4 -32. Dendrocopos medius + A 9-10 2 50-6033. Emberiza cirlus + + + A/C 9-12 2 -34. Emberiza caesia + + + A/ÌÁ 5/7-8 2 -35. Emberiza melanocephala + + A/C 5-7 3 -36. Erithacus rubecula + + + - 10-3 4 -37. Falco vespertinus + + - 5 2 -38. Falco tinunculus + + + MA - 3 5039. Falco eleonorae + - 5-9 2 -40. Ficedula albicollis + + + C/A 3-4 2 -41. Ficedula semitorquata + C 3 1 -42. Ficedula hypoleuca + + A/C 3-4 2 -43. Fringilla montifringilla + + A/C 11 2 -44. Fringilla coelebs + + + A/C 10-2 4 -

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45. Galerida cristata + + + A - 4 >7046. Garrulus glandarius + + MA - 3 6047. Hippolais olivetorum + + + A/C 5-8 2 -48. Hippolais pallida + + MA 5-8 3 -49. Hirundo rustica + + + - 5-9 4 -50. Hirundo daurica + + - 5 3 -51. Ixobrychus minutus* + MA 5 1 >8052. Jynx torquilla + + A 9 1 <5053. Lanius nubicus + + A/ΜΑ 5-9 2 -54. Lanius senator + + + A/ΜΑ 9/5 2 -55. Lanius collurio + + + A/ΜΑ 8-10 3 -56. Loxia curvirostra + ΜΑ 9 0 8057. Lullula arborea + + + A 10-11 1 -58. Merops apiaster + + A/C 4-5/9 4 -59. Millaria calandra + + A/C 10/4-5 2 6060. Motacilla alba + + + A 4-5/9 1 <3061. Motacilla flava + + + A/C 4-5/9 2 40-5062. Motacilla cinerea + + + A 5-9 1 5063. Muscicapa striata + + C 10-12 3 >1064. Nycticorax nycticorax* + A 9 1 6065. Oenanthe hispanica + + + A/ΜΑ 5-8 3 4066. Oenanthe oenanthe + + + C 5-9 3 <3067. Oriolus oriolus + + + - 8-10 3 -68. Otus scops + + A/C 5 3 -69. Parus caeruleus + + + C 5/9-11 2 -70. Parus lugubris + A 3 2 >7071. Parus major + + + - - 4 -72. Passer montanus + + + A/C 5 2 >6073. Passer domesticus + + + A/C - 4 -74. Petronia petronia + A/C 7/9 1 >6075. Phoenicurus ochruros + + + A/C 10-12 3 -76. Phoenicurus phoenicurus + + ΜΑ 4-10 3 >6077. Phylloscopus collybita + + + - 5/8-10 4 -78. Phylloscopus trochilus + C 9 2 5079. Pica pica + ΜΑ/A - 2 -80. Prunella modularis + + MA 10-11 2 >7081. Regulus ignicapillus + + MA 10-1 1 >6082. Regulus regulus + MA 10-12 2 >6083. Saxicola torquata + + + A 5/9 1 8084. Saxicola rubetra + + + A/MA 5/9 3 >6085. Scolopax rusticola + + + A/C 11-12 3 -86. Serinus pusillus + MA 5 0 6087. Serinus serinus + + + A 5-7/11 3 -88. Sitta krûperi + MA 5 0 >7089. Sitta newmayer + + MA 5-7 1 <3090. Streptopelia turtur + + + - 5-8 3 -91. Sturnus vulgaris + + + C 10-2 4 -92. Sylvia atricapilla + + + A 9-4 3 >6093. Sylvia curruca + + + MA 9-10 3 -94. Sylvia hortensis + + + A/ MA 5-7 3 -95. Sylvia communis + + + MA /A 9-10 3 -96. Sylvia melanocephala + + + MA /A 10-11 2 5097. Sylvia cantillans + - 5-7 2 7098. Troglodytes troglodytes + + + A/MA 10-2 4 -99. Turdus merula + + + MA 10-2 4 -100 Turdus philomelos + + + - 10-3 4 -

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101 Tyto alba + + MA 11 2 >60102 Upopa epops + + + A 5/9 2 -

* = Observed in olive groves near wetlands (Kalloni bay, Lesvos)

Insect collection

Three sampling expeditions were organized for specimen collection during the spring period (April-May 1993). Specimen collection was carried out for the same period of time (1.30' hours) using the same techniques (sweep and boxing) and at exactly the same time (06:30-08.00). The results are shown in table .4. It was observed that in the abandoned olive grove the number of species varied between 33 and 37 whereas in the olive groves abandoned and under grazing the number of species ranged between 19 and 22. The lowest number of insect species was observed in the cultivated olive grove (15-16 species). Insect species abundance in the abandoned olive grove is almost twice as high as in the other two categories.

Table 4: Insect species inside different olive grove categories

Olive grove categoriesAbandoned & under grazing

Abandoned Cultivated

Visit 1st 2nd 3rd 1st 2nd 3rd 1st 2nd 3rdInsect typeFlying insects 13 12 14 18 22 20 9 10 10Ground insects 6 8 8 15 14 17 7 5 6Total 19 20 22 33 36 37 16 15 16

Most of the specimens collected were living permanently inside the abandoned olive grove habitat. Some specimens were regular visitors (for food or protection) and few were just passing by.

The following trapping methods were used: Sweep net (vegetation beating technique and individual collection) Interception traps Pitfall traps Attraction traps Water traps BoxingFour collections were made: The 1991, 1992 and 1993 Skyros island collections

and the 1993-94 Lesvos island collection. Species identification was carried out in collaboration with the Universiteit van Amsterdam, Instituut voor Taxonomische Zoologie, Afdeling Entomologie. The insect classes are given in table 5. A total of 358 insect specimens (and 30 other arthropods) were collected. These specimens were classified into five classes and 125 families, indicating a diversified insect community.

Table 5: Arthropods inside the olive groves with emphasis on the Class Insecta.

Phylum Arthropoda

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Classes/Orders No of species

Classes/Orders No of species

Class Crustacea Class Insecta or HexapodaOrder Isopoda 2 Sub-Class ApterygotaClass Diplopoda 1 Order Thysanura 1Class Chilopoda Order Collembola 1Order Lithobiomorpha 1 Sub-Class PterygotaOrder Scutigeromorpha 1 Order Ephemeroptera 2Order Scolopendromorpha 1 Order Odonata 3Class Arachnida Order Orthoptera 19Order Opiliones 1 Order Dermaptera 2Order Scorpionida 1 Order Dictyoptera 4Order Chelonethida 1 Order Isoptera 1Order Aranea 15 Order Hemiptera 48Order Acarina 1 Order Neuroptera 15

Order Coleoptera 76Order Trichoptera 2Order Diptera 52Order Lepidoptera 70Order Hymenoptera 62

The Shannon index (H’)

The diversity of woody species in the abandoned olive groves and natural ecosystems of the islands was counted. Below is a list of plants that were considered “woody” by convention. According to the classification method of the researchers Koutsidou (1994), Mardiris (1991), and Giourga (1991), many biannual or perennial herbaceous plants, even if they have a woody part above ground, are not considered woody.

Table .6. The “woody” species in olive groves

Quercus coccifera Asparagus acutifolius CistaceaePistacia sp. Philyrea angustifolia Olea sp.Spartium junceum Anthylis hermaniae Rubus sanctusPhlomis fruticosa Sarcopoterium spinosum Origanum sp.Ceratonia siliqua Capparis ovata Lonicera implexaEuphorbia dendroides Ballota acetabulosa Thymus capitatusRosmarinus officinallis Anagyris foedita Genista acanthocladaPyrus amygdaliformis Sanguisorba minor Rubia tenuifoliaOsyris alba Alianthus altissima Lotus sp.Salvia sp. Satureja thymbra Lavandula stoechasPrasium majus Teucrium sp. Micromeria sp.

The general tendency is to consider as woody the perennial bushy or semi-bushy biotic types and, of course, all Phanerophyta.

If woody species are to be sampled, first of all they have to be present. Therefore, the cultivated olive groves, and the recently abandoned ones, which have only herbaceous vegetation, were excluded from sampling.

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The Shannon index for biodiversity was calculated for Skyros and Lesbos. In each island there was a sampling from 10 olive groves –10 sampling areas in each of them– for the calculation of the average biodiversity. The olive groves were chosen according to the degree of abandonment. The biodiversity was counted in groves of long-term abandonment, where the characteristics of cultivation were totally extinct and the state of present vegetation was a result of natural establishment and succession. The biodiversity in the wider area of these olive groves, the “natural” ecosystem, was also counted. Therefore the two types of ecosystem can be compared.

Table .7. The Shannon biodiversity index in sampled areas of each island.

SKYROS Isl. LESVOS Isl.Natural ecosystem

Olive Groves

Area Natural ecosystem

Olive Groves

Area

1,966548 2,000756 Gerouli 1 2,068742 1,960955 Pyrgi 12,428071 2,318988 Lakka 1 2,466892 2,012338 Lagada 12,001266 2,391804 Lakka 2 1,936422 2,042057 Lagada 21,888642 2,423561 Lakka 3 2,568924 2,160512 St. Ermogenis 11,73393 2,430964 Aspous 1 2,663426 2,265485 Taksiarxis 12,294244 2,434508 St. Antonios 1 2,903348 2,354392 Pyrgi 22,40795 2,551049 St. Antonios 2 2,269856 2,366392 Taksiarxis 21,817082 2,609854 Aspous 2 2,67654 2,380967 Pyrgi beach 12,065482 2,688163 Gerouli 2 3,006502 2,4635522,463552 Loutra2,60583 2,688731 St. Antonios 3 2,789621 2,749091 Pyrgi beach 2

Two columns of indices have been added, one from the natural ecosystems of the Greek mainland and one from reforested areas.

Table .8. Shannon biodiversity indices for ten areas of the Greek mainland, altitude <500 m. (natural ecosystems and reforested areas) (Mardiris, 1991).

Natural ecosystem

Reforestation Area Altitude

(Η') (Η') (m)2,136754 2,062308 Tristinika 502,434708 1,163377 Νew Marmaras 400-5002,563319 0,322858 Rapsani 5002,589742 0,959738 Vasilika 752,738144 1,711652 Stylida 100-1502,928557 1,162053 Nafpaktos 752,935315 2,282507 Kavala 4003,220291 1,02668 Atalanti 2503,23762 1,95844 Pteleos 2103,300309 2,504816 Ermioni 30-50

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Figure .1. Shannon biodiversity index (H’) for ten samples from olive groves and natural ecosystems in the research areas and from natural ecosystems and reforested areas throughout the mainland (see text). (Series 1: Skyros olive groves Series 2: Skyros natural ecosystem Series 3: Lesbos olive groves Series 4: Lesbos natural ecosystem Series 5: Natural ecosystems in Greece Series 6: Reforested areas in the mainland of Greece).

We can see a few of the index “tendencies” in the sampled areas. Some points made from the Figure 1: The natural ecosystems of the Greek mainland present the highest figures for the biodiversity index, a predictable fact mainly due to climatic factors and bioclimatic growth zone. The reforested areas, as expected, present the lowest figures of H’, because usually they are dominated by some pine species which creates thickets of the same age and is strongly competitive, limiting all efforts of natural regeneration of preexisting woody species. The natural ecosystem of Skyros presents relatively low figures of H’, which are justified by the pastoral nature of the island and the inevitable overgrazing, caused by 50.000 sheep and goats, in the 193 square kilometers of non agricultural land (Ksanthoulis, 1992). The abandoned olive groves of Skyros present a slightly higher biodiversity index compared to those of Lesbos. This can be justified by the fact that olive cultivation in Skyros was never as intensive as it has been in Lesbos. Therefore, in Skyros there is olive groves abandoned longer than those in Lesbos. The Shannon biodiversity index in the natural ecosystems and olive groves of the islands seem to fluctuate within a particular figure area, while the same index for the natural ecosystems and reforested areas in the Greek mainland seems to fluctuate within another figure area. The figures for the natural ecosystems of Lesbos are considered normal for Mediterranean island ecosystems.

Discussion

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In the Greek islands the most common “natural” ecosystems are the degraded “machi” and the areas of phryganic vegetation. In the best of cases maybe some scattered areas of pine forest trying to recover from the last fire.

On the other hand, the most common tree cultivation in the islands is olive cultivation. So, there are non productive olive groves of long-term abandonment that offer what a forest would, but to a greater extent than other areas designated as forests. Their contribution to the ecosystem consists of: Soil retaining due to ground coverage. Enrichment of the aquifer through the controlled penetration of precipitation due to flow retaining by vegetation. Refuge and food for the local fauna. Conservation of biodiversity. Improvement of the aesthetics of the surroundings.And all of the above are found in sites that are marginal, difficult to access,

mountainous, etc.After the collection and the process of all the data above, we considered that it was

of high importance to pay more attention to the need for continuous presence of the olive groves in the Aegean islands. It seems erroneous on the one hand to destroy the olive groves by cutting, fire and overgrazing and on the other hand to emphasize continuously the need for reforestation. It is therefore suggested that olive groves be maintained as ecosystems in the Aegean Islands even after their abandonment.

REFERENCES

ANTHOPOULOU, T.,1993. The olive tree grove in Mediterranean islands. In: Insula (International Journal of Island Affairs) 2: 55-61.

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