Natural history of Chrissi Island (Crete) in one day
A report on the field trip to the island during the COMENIUS NaTurE meeting in Ierapetra (25th – 29th September 2012) By Thomas Gerl, Maria Sourgiadaki & Darja Silan
Introduction Chrissi island is located about 15 km south-east of the Crete mainland. You can reach its natural harbour Vougiou Mati on the south side by boat from Ierapetra in about 45 minutes.
Figure 1: Map of Chrissi Island1
The name of the island in Greek means “golden” and is derived from the colour of the sand dunes and beaches. In recent times the island got a special protection status as an "area of intense natural beauty", because of its unique vegetation and marine wildlife. In spite of these conservation aspects, the beaches of the island – especially on the northern shore - are used for touristic purposes and quite a lot of sun hungry people enter the island each day during the holiday season.
Figure 2: Vougiou mati, at the south
1
http://www.chrissi-island-crete.com/map-and-factfile/
Geology and geomorphology Chrissi island covers an area of 5km². It extends up to 5km from east to west. On its narrowest place it only has a width of a few hundred meters from north to south. Kefala - the highest peak reaches 31m above sea level. The island was mainly formed by volcanic activities, so rocks of solidified lava are present all over the plains and hills. You can find periotids, diabases and gabbroes everywhere on the island:
Figure 3: Volcanic rocks present on the island: periotid (left), diabas (center), gabbroe (right)
These volcanic rocks lie on a base of calcareous sandstones that form the beaches and are continuously eroded by the salty water and the blowing wind.
Figure 4: Sandstone areas (left) are vulnerable to erosion caused by water (center) and wind (right)
These sandstone layers contain a variety of several different fossilized species, mainly mussels with diameters that can reach more than 10 cm. As these petrified organisms are all marine species, it is obvious that either the whole island was raised above
the sea level or the level of the Mediterranean sea dropped in the last couple of thousand years. The continuous erosion of the sandstone is the reason why most of the island’s central part is covered by sand dunes reaching heights of more than 20m above sea level, although most of them are less than 10m high. The steady wind is transporting the sand from the southern shore to the northern part of the island.
Figure 5: Sand dunes at the center (left) and the western slope of the island (right)
The volcanic slopes of the smaller eastern and larger western part of the island are not as heavily covered with sand as the central part. This might be due to the fact that these areas are a little bit higher than the central part of the island and so the wind deposits its sandy load more steadily in the lower areas.
Figure 6: At the north side of the island, area less covered with sand
Fossile records In the northern part of the island, on the sea shore, there are many remains from the past. Perfectly conserved fossils of sea shells (Bivalvia) are seen next to the shore line and are uncovering from the different types of stones. Like modern sea shells, fossile bivalves can be many shapes. In life, bivalve shells are made from layers of crystals of the minerals calcite or aragonite, which are the two different mineral forms of calcium carbonate (CaCO3). Fossil bivalves were formed when the sediment in which they were buried hardened into the rock. The layers from the marine deposits were probably lifted up by volcanic activities.
Figure 7: Fossils of molluscs-sea shells (Bivalvia)
Climate The closest weather station recording temperature and precipitation of the area is located in Ierapetra on the Cretan mainland. Although the microclimate of Chrissi island might be a little different due to its position in the Mediterranean sea, the general climate is very similar to that of Ierapetra: Mean temperature:
Rainfall:
Wind:
Figure 8: Climate data of Ierapetra2
The climate is characterised by long dry periods during the summer months and some rare but heavy rainfalls in the winter 2
http://www.hnms.gr/hnms/english/climatology/climatology_region_diagrams_html?dr_city=Ierapetra
time. In the summer of 2012 the period of no rain at all lasted 5 months. The maximum temperatures in summer time can exceed 40째C. As there is almost no forest cover, only few shady areas exist to keep moisture. Most of the precipitation evaporates quickly or drowns in the sandy soils that cannot keep great amounts of water. Concerning these climatic factors it becomes obvious that the natural fauna and flora must be adapted to extreme dryness.
Flora The island can be divided into several different zones of vegetation: Salt marches and salt pastures
Sea cliffs
phrygana Dry grassland
Coastal dunes with Juniperus spp. maquis
Figure 9: Map of the vegetation on Chrissi Island3 3
From http://www.junicoast.gr/
Vegetation of the beaches on the North side of the island The immediate coastline is free of vascular plants until some halophytic species appear:
Figure 10: Vegetation transect from the coastline to the dunes at Chrissi Island (Crete)
The spermatophyte growing closest to the shore is Sarcocornia fruticosa that grows in small bushes in the shelter of sandstone pits. Further away from the beach Zygophyllum album with succulent leaves joins the flora of the sandy beaches. Going even further away from the shore, some other salt tolerant species like Pancratium maritimum, Euphorbia paralias and an undetermined Chenopodiaceae appear in the sand.
Figure 11: Pancratium maritimum (left), Euphorbia palias (center), undetermined Chenopodiaceae (right)
Unfortunately man introduced some neophytic plants on the island. Next to the tavern on the north shore Caprobrotus acinaciformis grows , a plant from the southern part of Africa and an unknown Tamarisk species (Tamarix sp.).
Figure 12: neophytes on the northern coast line: Caprobrotus acinaciformis (left) and Tamarix sp. (right)
Shrubby vegetation The eastern and western part of the island is characterized by an open bushland with a vegetation cover of less than 50%. Between the heathland species large areas of open soils are visible and volcanic rocks are scattered all around the place. As this study took place at the end of the dry season, it was not possible to find and identify more species, because most of the species flower earlier in the year.
Figure 13: Shrublands with a high percentage of open soil in the western part (left) and with intermingled grasses in the eastern (right) part of the island.
Forests The most impressive part of the flora is to be found at the central part of the island. Due to the microclimate and special edaphic factors, some tree species can cope with the dry climate and the poor soils of the island. The most important tree species at the sand dunes are cedar (Juniperus macrocarpa) and juniper (Juniperus phoeniceum). What makes this Juniperus forest special is the fact the Juniperus microcarpa is rarely found on sand dunes and on the other hand a mixed forest of Juniperus microcarpa and J. Phoeniceum is not very common in Greece.
Figure 14: Juniperus macrocarpa (left, center) and Juniperus phoeniceum (right)
Due to the climate of the area these trees grow very slowly and do not get large crowns. The average height of the trees is about 37m, but some single individuals observed in the eastern part of the island can grow up to 10m. The roots of these trees are very important to prevent the erosion of the dunes, because they stabilize the fragile regime of the sandy soils. On the whole island it is obvious that due to the abiotic factors of the island the trees are struggling to survive and many dead trees or trees with dead parts are present. Figure 15: Dead parts of trees on the ground
Fauna The most interesting part of the Fauna is related to the Mediterranean sea. The beaches of Chrissi island possess a large variety of mollusc species, so a lot of seashells are present.
Figure 16: instead of sand, seashells!
During the short survey of the island only a few species could be collected and identified:
Figure 17: Collection of molluscs found at the north shore of Chrissi Island.
Besides these molluscs there are also some species of sea urchins present at the spill of the Mediterranean Sea.
Figure 18: Different sea urchins from the northern shore of Chrissi Island Regullaria (on the left) and Irregularia (on the right, sea urchin that normally lies burried just beneath the sand)
Birds and other animal species can be found on the island. We saw a bird of the Perdix species running on the sand and we also found the skin of an unpoisonous snake, Telescopus fallax. Figure 19: Silver gulls
Figure 20: sheep on the island
Human activities on the island Nowadays the island is uninhabited. But there are daily cruises to the island as it is a destination that attracts many tourists during the period from May to October, due to its unique natural beauty.
Figure 21: at the harbour of the island
Local people visit the island less, as it is said that the less they visit it the more it is protected. Nevertheless, you can find camping proofs around the island despite the fact that camping is not allowed... A tavern that used to offer basic facilities has recently been demolished and local authorities try to control the use of the island so that it is protected more. Human activities on the island used to be present from ancient times. At the western part of the island there are archaeological excavations of the Minoan era settlements, where they used to extract the red-purple dye “porphyra� from sea snails.
Figure 22: The excavations remain covered
Close to the church of Agios Nikolaos at the west, there is an area where some 60 years ago people used to grow wheat and watermelons. They collected rain water in a tank for irrigating the crop. The construction for distributing the water still remains there and the landscape is more or less barren. Figure 23: The construction for irrigation
A few meters away there is a covered well with semi-saline water and an old abandoned well with water and plants growing in it. As the fresh water was very important for different human activities on the island, the salt presented the same value. People from Ierapetra were coming to the island for collecting salt from shallow basin- small lake formed by sea water floods coming in spring time. During the long dry summer period water evaporated from the basin and the salt crystals remained as the sediment on the bottom. We can confirm that the taste of this salt is very good.
Figure 24:The salt pit (on the left) and details from the salt in it (on the right)
Chrissi Island is unique in its beauty and it should be protected with high legislation standard for natural parks. As it is an island, the sea is bringing up a lot of plastic and other waste. On the other hand the exploitation of the island for touristic purposes leads to some temporary “residents� as the old computer in the picture below.
Figure 25: some waste on the island can remain there for ever
Because of the strong winds, some waste is transporting into inner parts of the island. It would be necessary to organise frequent shore cleaning especially after the winter high tides.
Figure 26: The natural beauty needs protection
As people’s interest in preserving nature is growing we can look into the future with the hope that future generations also will be able to enjoy the rare beauty of Chrissi island.
Additional Literature http://www.chrisi-island.gr/en/vegetation.html http://chrissiisland.com/?page_id=107 http://en.wikipedia.org/wiki/Ierapetra http://www.ierapetra.net/chrissi.html Kalust Paragamian (2000): “The island of Chrissi”. Municipality of Ierapetra. http://www.junicoast.gr/ http://uaeco.biol.uoa.gr/files/PDF/P_G08.pdf