Ecological Territories

Transcription

1 1 Module # 2 - Ecology of Survival Objectives To familiarize the learner with ecological territories and the key survival factors associated with them. Expected Outcomes:?? Describe the ecological factors of survival?? Determine the type of ecological territory wherein they find themselves?? Describe the key survival factors associated with ecological territories Pre Test Question 1. Which of the following is not an ecological factor? a. Humans b. Plants c. d. Rainfall e. f. Soil g. Sunlight h. Wind Question 2. Which perspective looks at the way ecological territories are shaped? a. The habitat perspective b. The geomorphologic perspective c. The Vegetation type perspective d. The climatic region perspective

2 2 Introduction The ecological territories in Southern Africa are so diverse and varied that many people refer to it as the land of contrasts. Southern Africa includes the countries of Botswana, Namibia, Zimbabwe, Mozambique, Lesotho, Swaziland and South Africa. To obtain an understanding of ecological territories it will be useful to look at the area from different perspectives. There is the perspective of plant life where the types of plants in the region determine its inhabitants. This we call the vegetation type perspective. Then there is the habitat perspective, which look at areas according to the types of liveable environments it contains. This may be a mixture of specialised plant types, ecosystems and landforms. An example would be a distribution map for birds or animals. It will include specific vegetation areas like mountain-fynbos (heather-like plant type) or miombo-woodland (broad-leafed trees) as well as ecosystems and land forms like wetlands, sandy plains and coastline. Another perspective on territories is the geomorphologic perspective. In this instance we look purely at geomorphologic formations or landscapes like mountains and rivers. Lastly there is the climatic region perspective which looks mostly at rainfall in the regions. Because all these perspectives are very closely related and in most cases in interaction with each other, we will look at them individually but only at those aspects within them related to survival. Ecological Factors In survival ecology the most important factors that are in interaction with each other are: Biotic (living organisms)?? Humans (ourselves)?? Plants?? Abiotic (non-living factors)?? Rainfall and water?? Substrate/Surface (soil and terrain)?? Sunlight and heat?? Winds and wind-chill

3 3 The above factors will differ from territory to territory and for each unique territory there will be unique combinations and intensities of ecological factors. Ecological factors determine the way we:?? Find water?? Find food?? Find direction?? Move through the area???? Protect ourselves against the elements?? Protect ourselves against animals and other dangers?? Find or construct shelter Vegetation types It is important to know that different plants are found in different biomes. A biome is a distinctive vegetation and climatic region. In a later module we will deal with specific usable plants in each biome. Southern Africa has seven different biomes each representing different plants (in many sub-divisions!) with unique features that favour the area in which it exists. Vegetation type is one of the most popular indicators of ecological terrain to scientists and naturalists because it corresponds to factors like rainfall, altitude and soil types. It is also obvious from the table below that the green, moist areas are in the east and the dryer more arid areas are in the west. It is possible to survive in any of these biomes but some are easier to survive in, while others are maybe more dangerous. In fynbos for instance you may be at the top of the food chain whilst in savanna you d be glad to hang in the middle with the baboons. In the desert however you d wish you could find the food chain!

4 4 Table 1. Biome (Vegetation Type) Forest Savanna Thicket Grassland Desert Karoo Fynbos Position and Distinctive features Occurs mainly in the high rainfall (eastern) areas of Southern Africa. On the eastern escarpment of South Africa and the eastern mountain ranges of Zimbabwe we find mountain forest. To the south the forests are confined to the south and east coast. Another form also found is dune forest in pockets along the KwaZulu-Natal and Southern Mozambique coastlines. Distinctive features of forest are the high impenetrable canopy of tall trees with jungle-like undergrowth like large ferns, shrubs and climbers. To the north-east lies the moist savanna including Zimbabwe, Southern Mozambique and the northern parts of South Africa. Botswana and north-eastern Namibia are, however, famous for their arid savannah (Kalahari). Savanna is mostly a mixture of small to medium trees, grassland and scrubland. The canopies of trees are much more open than forests. Water may be found in temporary pans, dry riverbeds and certain plants. Thickets refer to impenetrable, thick bush and scrub found mostly on the southern and eastern coastlines and along river valleys in the interior. An interlaced mosaic of small trees, shrubs and undergrowth is distinctive of thicket. Water may be found in river beds (riverine thicket) or in small streams (valley thicket). The term Bushveld loosely represents savanna and thicket. Grassland can be found on the highveld plateau of central and eastern South Africa and the whole of Lesotho. Distinctive feature is the absence or sparseness of trees. Water may be found in natural springs, marshes, swamps and lakes. The extreme western strip of Namibia is desert. Shifting coastal sand dunes and hard gravel plains inland would indicate that you find yourself in a desert. Plant cover is sparse and only specialised plants can survive the dry conditions. Water is very scarce but may be found in coastal precipitate (fog, mist), specialised plant parts or, rarely, in natural springs or pans. The Karoo of the Western Cape and central strip of Namibia is a semidesert area with stunted woody scrub and low succulents. The area is mostly stony with low flat-topped hills. Water may be found in specialised plant parts or rarely in natural springs. The smallest of the world s six floral Kingdoms which is found almost entirely within the Western Cape boasting in excess of 8500 plant species. Around the southern coastal tip of South Africa right up to Port Elizabeth. It looks like a Mediterranean heath-land with fine leafed heather, proteas and restios (reed-like grasses). Water may be found in mountain streams, fog, mist or coastal marshland.

5 5 Key Survival Factors in Different Biomes Forest Trees are high and fruits are difficult to come by (except for fallen fruits) High diversity of useful insects More sheltered than other biomes against the elements but cold exposure or wind chill may occur Building materials available but difficult to work with Water potential high due to high rainfall areas Medium to difficult depending on thickness of undergrowth and slope Difficult, because you can mostly not see the sun and stars. Low, obscured by tree trunks and undergrowth Getting lost, stinging insects, hypothermia in mountains Savanna High diversity in useful plant life. Thorny plant species make it easy to form a protective enclosure against predators High diversity in useful animals but dangerous animals and predators may also be present High risk from all elements Relatively easy to build a shelter with branches and tall grass Water potential medium (moist savanna) to low (Kalahari) Relatively easy Relatively easy except in mopane forest or miombo-woodland Good in winter and medium in summer due to growth Predators, heat exposure, dehydration, hypothermia at night Thicket High diversity in useful plant life. Thorny plant species makes it easy to form a protective enclosure against predators High diversity in useful animals High risk from all elements Relatively easy to build a shelter with branches Water potential medium Impenetrable bush makes it difficult to travel Relatively easy very low (can t see more than a few feet around you) Stinging and biting animals, heat exposure, dehydration

6 6 Grassland Low diversity in useful plant life. High diversity in insect, bird and small mammal life High risk from all elements Difficult but possible to build a shelter from grass or reeds. Water potential is medium to high due to rainfall and surface water Easy Relatively easy high all round, green patches may indicate water or shelter Heat exposure, Chill factor, dehydration Desert Low diversity in useful plant life. Low diversity in useful animal life, but has dangerous snakes, scorpions and spiders (All of them are edible though) Exposed to severe cold at night and severe heat during the day Difficult to find, may have to dig in soft sand and bury yourself or look for rocky overhang or cave Water potential is very low Difficult on dunes and loose sand but easy on gravel Relatively easy high all round, green patches may indicate water or shelter Heat exposure, Chill factor, dehydration, venomous creatures Karoo Low diversity in useful plant life. Low diversity in useful animal life but has reptiles and rodents Exposed to severe cold at night and severe heat during the day Difficult to find, may have to look for rocky overhang or caves Water potential is very low Relatively easy except in very rocky places Relatively easy high all round, green patches may indicate water or shelter Heat exposure, Chill factor, dehydration, venomous creatures

7 7 Fynbos Useful plant life may be found. Low diversity in useful animal life but has reptiles and rodents Exposed to all elements and in mountains conditions can be severe s can be built with grasses and bushy material or, in mountainous areas, caves and overhangs may provide shelter Water potential is high in mountains but low in sand flats Relatively easy except in mountainous areas Relatively easy except during fog or mist that may prevail for long periods of time high except during fog or mist that may prevail for long periods of time Heat exposure, Chill factor, dehydration, getting lost in mountains Habitats A habitat is a place or unique area that can sustain life. It is therefore similar to a home or home range. A rocky outcrop could be considered a typical habitat for leopards next to the plains because they may have a safe den there and may frequent caves or overhangs. A river on the other hand is a habitat for a range of creatures of which fish may be the most obvious. Certain creatures are adapted to survive in specific habitats and these habitats can be found in or close to any of the above vegetation types and include: Mountains and their associated structures?? Slopes (north, west, south or east facing) Northern and western facing slopes are normally warmer and dryer with fewer trees that are more widely dispersed. Southern or eastern facing slopes are normally moist and cool with more trees that are more closely concentrated. Importance: Rough guide as to north/west or south/east. It is also better to stay on cooler slopes and besides there is more shelter and opportunity to find food?? Rocky areas Large boulder areas that are well-drained and high in nutrients, certain plants abound, like for instance rock figs. Importance: Good for shelter and fruit trees but beware of dangerous animals with the same idea

8 8?? Plateau s Flat areas on top of mountains normally covered with grass Importance: Good vantage point and may make it easier for search party to spot you and or land to pick you up.?? Kloofs and valleys Well-shaded V shaped narrow ravines and valleys. May harbour moist forest or thicket vegetation types. Importance: Possible source of water in rocky pockets or mountain streams?? Caves Underground cavities due to water or wind weathering. Importance: Possible shelter and sometimes still have water, which weathered it in the first place Plains and their associated structures?? Rocky outcrops Boulder hills or granite outcrops with associated plants Importance: May contain useful plants. Caves and overhangs but beware of dangerous animals with the same idea?? Termite mounds Heaps or mounds (sometimes huge) built up by termites. Well aerated and rich in nutrients it supports plants like jacket plum and buffalo thorn trees. The tip of a mound sometimes bends to point north. Importance: Useful plants found on termite mounds. Helpful as a vantage point and to find direction. Termites are also a very good source of protein

9 9?? Different soil types Deep sandy soils or clay/turf soils. Sandy soils drain very fast and maintain plants with large leafs. Because the soils drain fast the plant takes on a large quantity of water very fast and the large leaves help them getting rid of the excess water. Clay or turf soils are more nutritious with small leafed plants [thorny acacia s]. Because water clings to the clay particles and is more difficult to absorb by the roots, these plants have to conserve water, therefore they have small leaves to prevent further water loss. Importance: Sandy soils drain very fast, are difficult to walk or run on and leave easy tracks to follow. Clay or turf soils hold water much longer and it is tougher and more difficult to track on. Waterways and surface water?? Wetlands?? Temporary pans?? Lakes and dams?? Rivers and streams A mangrove thicket is obviously a source of water and is therefore also a place where many organisms get together, making it useful as well as dangerous Coastal habitats?? Sandy shore?? Rocky shore?? Intertidal zones Importance: The coastlines of Southern Africa are great sources of food, in fact more so than the interior, but have the serious drawback that potable water is sometimes very difficult to find. Coastal habitats will be dealt with in detail in Module # 9 From the above it is clear that survival will differ from place to place. For instance, a sandy soil area will be totally different to survive in than around a rocky outcrop. Walking on sand in a mopane forest is tiresome and you can get lost more easily, whilst a rocky outcrop may harbour dangerous animals or unfriendly people although you may have a better view from there. Once again you will need to make decisions about the habitat you re in.

10 10 Geomorphology Geomorphology is all about the landscape and how it got to look the way it does. It relates to the processes and forces that changed the earth into the shape it has today. In the geomorphologic perspective we look at how habitats, such as mountains, formed (maybe through old volcanic working or through earth plate movements). This may help us understand and determine what kind of terrain to expect. Large valleys may be the result of ancient glacial working or from more recent river flows. A desert may be the result of losing topsoil due to over-grazing or it may be that the atmosphere changed climatically. Another Geomorphologic aspect of Africa is a rift valley of waterways, which stretches from Mozambique in the south right to the north of Africa, through the red sea and into Israel, and it supports a range of human, animal and plant communities. Significant geomorphologic features of Southern Africa would be: a. The dry desert and semi-desert (Karoo) in the west and central areas of the region. b. The Kalahari (arid sandy savanna) of Botswana. c. The Eastern mountain ranges of the great escarpment on the eastern border of Zimbabwe and the Drakensburg Range of South Africa. d. The Cape folded mountains in the south. e. The Highveld (temperate) region of the interior with its rolling hills and grasslands f. The northern waterways of the Cunene river, Okavango river, the Okavango swamp, Lake Kariba, Cabora Bassa dam and the Zambezi river. g. The central river belts of the Orange river, Vaal river, Crocodile and Limpopo rivers. From a geomorphologic point of view it is important to remember that water can be found in low-lying areas like the bottom of valleys, riverbeds and foothill basins. Large rock plates may also prevent water from flowing away, even if it is underground. On the other hand, high vantage points like mountains and rocky outcrops may provide for vistas in which you can spot the green tree line of a river, or the reflection on a lake, or even a man-made dam.

11 11 Climatic Regions As mentioned before the green, moist areas of Southern Africa are in the east and the dryer more arid areas are in the west. The eastern mountain ranges and coastal areas get the most rain (750 to 1500mm per year). Next to that the highveld and grasslands of the interior and south coast get about 250 to 750mm per year. The west and central areas are the driest with 0 to 250mm per year. It is also important to remember that the south-western parts get most of their rain in the winter with very dry summers and the north-eastern parts have rain in summer with relatively dry winters.