**8. Conclusion**

Platberg is a centre of significant biological diversity, with high species richness, vegetation and ecosystem complexity and a centre of genetic diversity and variation. It occurs as an island in the Grassland 'sea' and shares inselberg floral richness and endemism which can be tracked via the Afromontane archipelago-like string of inselbergs and mountains which stretch north through the Chimanimani Mountains, into Malawi, the East African Arc of Mountains via Tanzania and north through Ethiopia into Eurasia. It also shows a western tract via the Congo, Ivory Coast and Cameroon inselbergs and mountains.

The current vegetation patterns on Platberg reflect changes in palaeo-environmental cycles of cooling and warming which, since Miocene times have had the greatest influence on the texture and composition of plants and speciation on Platberg. Floristically and choriologically, Platberg has a grass composition showing transition between C3 high altitude grasses and C4 grasses, the latter favouring hotter temperatures, lower altitude and lower rainfall. It also has a significant composition of plant families using CAM, C3, C4 and metabolism. This floristic composition is shared by the DAC. Current trends towards climate change will alter the composition and species numbers of grasses as well as other plant families, which use these metabolic pathways.

Floristic and compositional connections extend up the Great Escarpment via a series of inselbergs as well along sheltered gullies into the Lebombo Mountains, and west via the Magaliesberg (Figure 8). Affinities are also shown in the Chimanimani Mountains, with attenuation in the Mulanje Massif and Nyika Plateau. Floristic connections are also shared with other inselbergs in west and central Africa and show extension along the Afro montane mountain region.

Climate changes have directly influenced the evolution, structure and composition of the vegetation of southern Africa, the main driving force possibly being orbital (Croll/Milankovitch) cycles (Kutzbach 1976; Bennett 1999; Muller & MacDonald 1999; Linder 2003). The most significant, relatively recent changes started in the Palaeocene (65 million years BP) with the Gondwana break-up. This started a cycle of erosion and uplift of the interior of southern Africa. Cycles of glaciations and interglaciation, cool wet, hot dry periods, influenced the environment and forced high speciation (Bennett 1999), still evident in the high species richness exhibited today in the flora of the DAC, Platberg and the Cape flora. At the start of the Quaternary (2.4 million years BP) the DAC and Cape Flora were much as they are today, but showed range extensions and contractions due to the longer, cooler, wetter 100 000 year glaciations, and the shorter, hotter, drier 10 000 year interglaciation periods.

Fire and the grazing by herbivores also helped shape the vegetation, with the greatest influence on the Grassland Biome. These cumulative effects, geological processes, climate

Platberg as well as the DAC. This long-distance dispersal by wind allows for crossing

Pollination by wind allows for gene flow between disparate areas (Cowling & Lombard 2002), which have different geology, soils, moisture availability and climate (Burke 2001, 2002; Linder 2003). The effects of wind to influences floristic composition and species richness over long distances and connect different regions is seen on the granite inselbergs in West African (Porembski et al., 1996), Namibian (Burke 2001), and Mulanje (Burrows & Willis 2005), basalt lavas of Platberg (Brand et al., 2010), the Drakensberg (Mucina &

Platberg is a centre of significant biological diversity, with high species richness, vegetation and ecosystem complexity and a centre of genetic diversity and variation. It occurs as an island in the Grassland 'sea' and shares inselberg floral richness and endemism which can be tracked via the Afromontane archipelago-like string of inselbergs and mountains which stretch north through the Chimanimani Mountains, into Malawi, the East African Arc of Mountains via Tanzania and north through Ethiopia into Eurasia. It also shows a western

The current vegetation patterns on Platberg reflect changes in palaeo-environmental cycles of cooling and warming which, since Miocene times have had the greatest influence on the texture and composition of plants and speciation on Platberg. Floristically and choriologically, Platberg has a grass composition showing transition between C3 high altitude grasses and C4 grasses, the latter favouring hotter temperatures, lower altitude and lower rainfall. It also has a significant composition of plant families using CAM, C3, C4 and metabolism. This floristic composition is shared by the DAC. Current trends towards climate change will alter the composition and species numbers of grasses as well as other

Floristic and compositional connections extend up the Great Escarpment via a series of inselbergs as well along sheltered gullies into the Lebombo Mountains, and west via the Magaliesberg (Figure 8). Affinities are also shown in the Chimanimani Mountains, with attenuation in the Mulanje Massif and Nyika Plateau. Floristic connections are also shared with other inselbergs in west and central Africa and show extension along the Afro montane

Climate changes have directly influenced the evolution, structure and composition of the vegetation of southern Africa, the main driving force possibly being orbital (Croll/Milankovitch) cycles (Kutzbach 1976; Bennett 1999; Muller & MacDonald 1999; Linder 2003). The most significant, relatively recent changes started in the Palaeocene (65 million years BP) with the Gondwana break-up. This started a cycle of erosion and uplift of the interior of southern Africa. Cycles of glaciations and interglaciation, cool wet, hot dry periods, influenced the environment and forced high speciation (Bennett 1999), still evident in the high species richness exhibited today in the flora of the DAC, Platberg and the Cape flora. At the start of the Quaternary (2.4 million years BP) the DAC and Cape Flora were much as they are today, but showed range extensions and contractions due to the longer, cooler, wetter 100 000 year glaciations, and the shorter, hotter, drier 10 000 year

Fire and the grazing by herbivores also helped shape the vegetation, with the greatest influence on the Grassland Biome. These cumulative effects, geological processes, climate

mountain valleys, from one isolated peak or inselberg to another.

**8. Conclusion** 

mountain region.

interglaciation periods.

Rutherford 2006), and quartzite of the Cape Fold Mountains (Linden 2002).

tract via the Congo, Ivory Coast and Cameroon inselbergs and mountains.

plant families, which use these metabolic pathways.

change, CO2 level fluctuations, fire and grazing are all responsible for the present day species richness and diversity recorded on Platberg and its parent vegetation of the Drakensberg. The Grassland Biome in South Africa is second largest of all eight Biomes (354 593.501 km²) after the Savanna Biome (412 544.091 km², Mucina & Rutherford 2006), with both Biomes providing an enormous sink for Carbon as well as climate amelioration.

Between 30–55% of the Grassland biome has already been transformed with only 5.5% protection. Grassland is under significant threat of continual transformation, the most severe is ploughing, which disrupts the soil and releases not only moisture, but also nutrients and Carbon (Mucina & Rutherford 2006).

Fig. 8. Platberg showing tracks of the major floristic influences (modified from Rutherford & Westfall 1994).

Undisturbed grassland provides a significant Carbon sink, and should thus be given priority status for conservation, which should include both the above ground and belowground grass and soil ecosystems (Retallack 2001).

Historically in South Africa, areas for conservation were not selected primarily for ecological reasons until the mid 1970's (and then only in the Cape), but were rather based on other criteria, such as national strategically protection of the watershed around dams; fragmented forest areas to protect the water sources higher up in the mountains, or politically determined boundaries such as the Kruger National Park. It was only between 1971 and 1982 in the Cape, that a few wilderness areas were established for scientific research in natural ecosystems, aesthetic values they engendered and physical and spiritual opportunities they afforded (Rebelo 1992). Biogeographical considerations such as fynbos being 'islands' surrounded by forest were used as well as critical plant population size and habitat. These parameters plus total land surface were selected in determining conservation areas. It was found that for mountain areas, the minimum statuary size for reserves should be at least 10 000 ha (Rebelo 1992). Human population growth and increased urbanisation are seen as two major threats to natural ecosystems, with the implications for conservation of the effects of unrestricted human population growth being considered (Rebelo 1992; Ferrier 2002).

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The scale of human impact on the biogeographical distribution of plants and animals will only continue to grow globally, but specifically in Africa, with the continued existence of many plant and animal species more dependant on human social, rather than on physical environmental factors (Meadows 1996; Anderson et al., 2001; Mutke et al., 2001). The African landscape, in particular East Africa, has had a long history of influence by humans, i.e. the Savanna and Grassland Biomes (Meadows 1996). Globally, and in the context of the use of resources and climate change in Africa, the human species now exerts an influence on all other species of organism, which in its scale and intensity is critical in the future evolution of the African flora and fauna (Kingdom 1989; Meadows 1996; Anderson 2001; Mucina & Rutherford 2006).

The conservation value of Platberg is significant: is a link between high altitude C3 grasses and lowland C4 grasses. It is also the best-preserved continuous high altitude grassland within the Grassland Biome and has escaped agricultural activity which giving the site a unique status, and leaves enormous scope for future research (Smith & Young 1987). Platberg is an excellent natural history laboratory, which connects the present day environment with geological, palaeo-environmental and evolutionary processes from modern Holocene to Jurassic times (Scott et al.1997; Anderson 2001; Linder 2003; Mucina & Rutherford 2006).

## **9. Acknowledgements**

National Geographic (Grant number 7920-05) for the generous funds without which the fieldwork and the study would not have been possible.

Snow on Platberg, Figure 4. Kind permission of Theunis Bekker.

Figure 8, Wetlands on Platberg is courtesy of Nacelle Collins.

#### **10. References**


The scale of human impact on the biogeographical distribution of plants and animals will only continue to grow globally, but specifically in Africa, with the continued existence of many plant and animal species more dependant on human social, rather than on physical environmental factors (Meadows 1996; Anderson et al., 2001; Mutke et al., 2001). The African landscape, in particular East Africa, has had a long history of influence by humans, i.e. the Savanna and Grassland Biomes (Meadows 1996). Globally, and in the context of the use of resources and climate change in Africa, the human species now exerts an influence on all other species of organism, which in its scale and intensity is critical in the future evolution of the African flora and fauna (Kingdom 1989; Meadows 1996; Anderson 2001;

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**6** 

**Biodiversity Loss in Freshwater Mussels:** 

The loss of biodiversity worldwide has been well documented for decades, and while much of the attention of the media and scientific community has been focused on terrestrial ecosystems, other biomes such as freshwater lakes and streams have received less consideration (Myers et al., 2000). Despite the current decade (2005-2015) being declared an International Decade for Action – 'Water for Life' by the United Nations General Assembly, freshwater ecosystems worldwide are as threatened as ever by the activities of a rapidly growing human population. Surface freshwater ecosystems only constitute 0.8% of the Earth's surface, yet they contain almost 9.5% of the Earth's known species, including as many as one-third all known vertebrate species (Balian et al., 2008; Dudgeon et al., 2006). The impact of human disturbances on this disproportionate amount of biodiversity has made the extinction rate in freshwater ecosystems equal to that of tropical rainforests

Because we depend on water both as a biological necessity and for the myriad of resources and services it provides us, over half of the world's population lives within 20 km of a permanent river or lake (Small and Cohen, 1999). Direct benefits and ecosystem functions of freshwater lakes, streams, and wetlands include providing sources of water for municipal and industrial use, irrigation, hydroelectric power generation, transportation corridors, recreation, and producing fish and other resources used for food and medicine. Freshwater ecosystems also provide many indirect ecosystem services such as water filtration, buffering against storms and flooding, cycling of nutrients and organic matter through the environment, and supporting ecosystem resilience against environmental change (Aylward et al., 2005; Jackson et al., 2001). These indirect ecosystem services have very real economic values. One study valued the ecosystem services of freshwater aquatic ecosystems worldwide at \$6.5 trillion

As human populations continue to develop aquatic resources to maximize a few of these anthropogenically beneficial services such as water storage, generation of electricity, and fish production, other environmental services that are less directly important to humans are being reduced or lost (Bennett et al. 2009). The reduction of these ecosystem functions can significantly alter an ecosystem's natural character. After more than a century of

USD, or 20% of all the world's ecosystem services (Costanza et al., 1997).

**1. Introduction** 

(Ricciardi and Rasmussen, 1999).

**1.1 Freshwater ecosystem services** 

**Importance, Threats, and Solutions** 

*Department of Biology, Texas State University, San Marcos, Texas*

Trey Nobles and Yixin Zhang

*The United States of America* 

