Transcript Chapter2
HISTORY OF BIOLOGICAL INVASIONS, CONTINUED GLOBALISATION AND THE INTRODUCTION OF GENETICALLY MODIFIED ORGANISMS HISTORY • In geological terms, invasions of species from one continent to another are true evolutionary processes, a bit like speciation and extinction. • Large-scale climatic and geographic changes cause massive movement and exchanges of flora and fauna. In some areas, whole floras have been replaced (di Castri, 1989). • At a smaller scale many organisms overcome physical barriers like oceans, mountains & deserts by moving on rafts of vegetation carried by rivers and marine currents, and long-distance wind transport (di Castri, 1989). HISTORY cont. • However, it is human occupation and migration that is seen as the driving force of many biological invasions, rather than geological or evolutionary change. • Since 1500AD, new man-made routes have been opened up across biogeographical realms, with the advent and improvement of transport and communication systems (di Castri, 1989). • Humans have migrated and colonized different continents. • Invasive species have followed in the tracks of human migrations, some being intentionally taken along with humans, but many hitch-hiking or being accidentally transported (covered in Chapter 4) to new areas. DRIVING FORCES OF EARLY INVASIONS (adapted from di Castri, 1989) BEFORE 1500 AD • Forest clearing for agriculture and livestock, with later intensification of agriculture by ploughing. • People moved around relative to food and shelter for themselves and their livestock (nomadism). • Islands and coastal areas were settled (eg. Corsica and Greece), and coastal trade started taking place. • Roman and Persian empires were established, communication and transportation systems were expanded, along with military expansion and occupation. BETWEEN 1500 AND 1800 • Exploration, discovery and colonization by Europeans of other continents. • Large colonies came to be under the rule of Europeans, establishing European-like agriculture systems. • Many Europeans tried to recreate “home” by introducing species that they were familiar with (wheat, barley, cattle, horses and sheep). • Establishment of new market economies. BETWEEN 1500 AND 1800 cont. • Revolution of food customs (increased use of tea, coffee, chocolate, maize, beef) • Slavery and missionary establishments • Intentional introductions of exotic species for botanical gardens and zoos, agriculture, forestry, fishery, or ornamental purposes. BETWEEN 1500 AND 1800 cont. • Australian aborigines arrived with the dingo, and Polynesians brought pigs, taro, yams, and rats (as stowaways). • These early colonists devastated local species with the introduction of new species, leading to many extinctions. • Large-scale emigration due to persecution during religious conflicts, wars, unemployment and famine 1800 – PRESENT • Improvement and development of transportation systems. Once steam-powered ships became common, more than 50 million Europeans emigrated between 1820 and 1930, taking with them plants and animals from home (McNeely, 1999). • Opening of inter-oceanic canals (eg Suez, Panama) • World wars and displacement of human populations • Tropical deforestation and resettlement schemes 1800 – PRESENT cont. • Afforestation of arid lands with exotic species • Increased urbanization • International interdependence of markets • Release of genetically modified organisms GLOBALISATION • The growth in global economic output during the 1980s was greater than that of the thousands of years from the beginning of civilization to 1950 (WRI, 1994). • One critical element of economic globalisation is the movement of organisms from one part of the world to another through trade, travel, transport and tourism. • Humans have moved organisms beyond their natural ranges for centuries, but the frequency and incidence of such movements were too limited to generate widespread invasions. With the increase in trade, travel and tourism, globalisation has increased the rate and distance at which species would naturally move. GLOBALISATION cont. • Many people welcome globalisation of trade, and increased income in many parts of the world lead to an increased demand for imported products. In most parts of the world, the majority of nutritional needs are met by species that have been introduced from elsewhere (Hoyt, 1992). As an example, over 70% of the world’s foods come from just nine crops – wheat, maize, rice, potato, barley, cassava, soybean, sugarcane and oats (PrescottAllen and Prescott-Allen, 1990), each of which is cultivated far beyond its natural range. GLOBALISATION cont. • With the increasing demand for imported goods, more land is cleared, ploughed and planted with introduced species. Because of this, there is a reduction in indigenous biodiversity, to be replaced by a limited range of agricultural crops. This is known as “biological pollution” (McNeely, 1999) or “biotic homogenisation” (McKinney and Lockwood, 1999). • “Biological pollution” reduces the diversity of crops and livestock and can increase their vulnerability to both native and exotic pests, often leading to the increased use of pesticides, which may have broad negative impacts on ecosystems (McNeely, 1999). GLOBALISATION cont. • Unique endemic species become extinct and are replaced by already widespread species. One effect globalisation is the local increase but global decrease in biodiversity, at species and genetic levels, with local areas also experiencing decreases in diversity at a later stage. Photo: Charl Cilliers Correspondence between human population growth and number of alien plants. Naturalized ruderal/weed plants (excluding trees and shrubs), and nonindigenous trees and shrubs (Sukopp and Wurzel, 2003). Chapter 1 Definitions Chapter 2 History, globalisation and GMOs Next Chapter 3 The human dimension Chapter 4 Pathways of introduction Chapter 5 Characteristics of invasive alien species Chapter 6 The ecology of biological invasions Chapter 7 Impacts of invasive alien species Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 12 I hope that you found chapter 2 informative and that you will enjoy chapter three!