As we saw in Chapter 15, the first national parks were developed in the nineteenth century. They were the forerunners of many nature reserves and wildlife sanctuaries. As the conservation movement has gathered momentum, in situ management of reserved areas has become the key strategy employed by conservationists in their efforts to secure the future of biodiversity. There are many types of reserves of different sizes: all are fragments within a matrix of surrounding territories that might have different land use. Considering the size, geographical location and ‘connectedness’ of lands set aside for conservation, how far has it proved possible to secure the future of endangered species and ecosystems? Also, what ‘strengths and weaknesses’ have been identified after more than a century of experience in managing reserves?

Reserve design

The theory of island biogeography proposed by MacArthur and Wilson (1967) drew on important earlier research by Preston and others (see Mann & Plummer, 1996). The theory explored the implications of the observation that species richness tended to be low on small isolated islands far from land. In contrast, biodiversity was often greater on large islands close to the mainland. On the basis of these ideas conservationists proposed a number of model systems for reserves and national parks.

The evidence presented in previous chapters makes it plain that human activities create profound and highly complex changes in ecosystems through the imposition of new selection pressures. Darwin predicted that selection favours those species and populations that have the necessary genetic variability to survive and prosper under changing conditions. In contrast, species and populations that lack the necessary Darwinian fitness for the new conditions are at a selective disadvantage, and are in danger of becoming extinct.

This chapter analyses the extinction processes at the population level, providing the necessary background to a key issue to be examined below. Can the extinction of species/populations be prevented by appropriate conservation management?

As a prelude to the discussion on extinction, it is important, as always, to understand Darwin's own view of the vulnerability of rare species and appreciate his insight that extinction is often the end point of a process of decline. In the Origin (Darwin, 1901, 79–80), he writes:

This chapter considers a number of questions relating to hybridisation and speciation in ecosystems disturbed by human activities. Many species of plants are currently endangered. If there are many extinctions in the near future, will new species quickly evolve to take their place? As a consequence of human activities, a large number of species of plants have been introduced accidentally or deliberately across the world. What are the consequences of such human-induced breakdown of geographical isolation between species? Agricultural landscapes cover a large area of the globe. What have been the microevolutionary effects of the interaction of crop, wild, garden and weedy plants? Finally, what are the implications for conservation of species hybridisation in anthropogenic ecosystems?

Will new species quickly evolve to take the place of those that become extinct?

Human activities produce many patchy and mosaic habitats. In situations where a genetically polymorphic species occurs in two or more adjacent habitats, disruptive selection is likely to take place and this could provide the setting for the early stages of speciation. An example shows the possibilities. In many parts of Britain, within the extensive pasture lands there exist islands of heavy-metal contaminated debris and spoil left by the mining industry. As we saw in Chapter 10, where a species occurs both on the mine debris and in the pasture, there is evidence of gene flow and disruptive selection. Pasture plants are heavy-metal sensitive and cannot grow on the mine: mine plants perform less successfully in the pasture.

In their introduction to the Plant Red Data Book of endangered species, Lucas and Synge (1978, 31) concluded: ‘Botanic gardens…are poised to play a major role not only in cultivating the [endangered] plants concerned, but also in their re-introduction, in habitat management and even in owning and maintaining small reserves for particular species.’ Moreover, they predict: ‘once the individual facts on threats, habitats sites and populations are known, successful conservation of most plant species is likely to prove far less difficult and costly than that of animals’. After 30 years, it is timely to review the role of botanic and other gardens in the conservation of endangered species, and to examine current views on these predictions.

The use of the phrase ‘poised to play a major role’ suggests that the use of botanic gardens for the conservation of wild endangered species represented something of a new direction for gardens in the 1970s and 1980s (Lucas & Synge, 1978). For what purposes were botanic gardens founded in the first place, and how have they developed historically? What have theoretical investigations and practical studies revealed of the ‘strengths and weaknesses’ of gardens in their proposed new role? Given the ‘costs’ associated with ex situ conservation, endangered species are generally grown in botanic gardens and arboreta. What are the likely consequences of such cultivation?

Herbivory in anthropogenic ecosystems

Microevolutionary insights have come from investigations of a number of different kinds of managed grassland (hay, pasture, lawns and sports turf), and also from arable lands and managed forests. While, at first sight, management regimes are very different, they all involve selective herbivory.

Managed grasslands, rangelands etc.

In such habitats, humans take a harvest directly from the sward, either through haymaking or fodder collection, or, indirectly, through the management of domestic, semi-wild and wild animals. From the plant's eye view, harvesting by cutting and grazing are quite different. Harper (1977) makes this point very clearly, when he notes that, in clipping or mowing, some portion of the sward is more or less evenly removed. In contrast, grazing is patchy, and animals differ in their behaviour. ‘The cow rolls her tongue round a bunch of grass and pulls…sheep bite leaves between the incisors of the lower jaw and a pad on the upper jaw whereas the rabbit cuts leaves with teeth on both jaws.’ In addition, Harper makes it plain that the un-eaten portion of the sward is impacted by grazing animals, in their deposition of urine and dung and their tramping of the vegetation. Thus, ‘grazing animals frequently sit, lie, scratch and paw on pasture in addition to walking, running and jumping on it’ (Harper, 1977, 449).

In The Variation of Animals and Plants under Domestication, Darwin (1905, vol. 390) considered an issue raised by Loiseleur-Deslongchamps in his book Les Cereales. As cereal crops have evolved under domestication, perhaps the weeds infecting the fields in which these crops have been grown have also changed. It is interesting to quote Darwin's reaction to this point and his cautious conclusion.

Human-influenced ecosystems are the arena for contemporary microevolution, and the increasing spread and intensity of human activities are major concerns for conservationists. It would be possible to assume that the historical and contemporary effects of human influences are so widely understood and appreciated that only a few paragraphs are needed at this point in the book. However, such an approach would fail to set the scene adequately for what follows. In a brief historical review, this chapter examines several major issues: (a) the environmental consequences of inexorable rise of human populations; (b) how changes in agriculture and technology have led to abrupt and gradual environmental transitions; and (c) how human activities have resulted in the widespread introduction of plants and animals into new areas across the globe. This chapter also considers the rise of public concern about the profound human impacts on the world's vegetation, animal resources and soil, leading to the development, in the post-Second World War period, of increased environmental awareness, focusing on human population growth (now at over 6 billion and projected to rise), habitat destruction, over-harvesting of natural resources, the extinction of species, the impact of pollution and the dramatic consequences of the widespread introduction of alien species across the world.

The origin of humans

Weber (2005) notes that only about 10% of the population of the USA fully accept a Darwinian explanation of the origin of humankind, many believing that the world and its plants and animals are of very recent origin.

I grew up in Stocksbridge, a small town in the Yorkshire Pennines between Sheffield and Manchester. Looking down into the valley, there were massive steel works, mines, coke ovens, blast furnaces, pipe works and rolling mills that polluted the air with fumes and smoke. The local river – the Little Don or Porter – was heavily contaminated close to its source. Slag and other wastes were dumped in the woodland downstream below the works. In the 1950s, our community was not alone in suffering from the effects of industrial pollution; indeed, the problem was widespread in South Yorkshire.

However, Stocksbridge had one important advantage not shared by many other towns. Looking down the valley the prospect could be depressing, but this was not the whole picture. Beyond the valley, the hills and valleys of the Peak District National Park came into view, offering some of the finest scenery in England, with farms, rough grazing, woodlands, moorlands managed for grouse shooting, and reservoirs that provided drinking water for Sheffield.

It was here, in an area of such contrasting land use, that I first considered the historical and ecological forces at work shaping the industrial landscapes and the moorland, woodlands and farmland of the National Park. In time, the scope of these reflections widened, for while recovering from some brief teenage illness, I first read Charles Darwin's Voyage of the Beagle (1839).

It is often erroneously believed that evolution is something that happened in the past. However, there is strong evidence that evolution is continuing at the present time, as plants face new selection pressures generated by human activities that destroy, damage, fragment and alter ecosystems. In a world grappling with anthropogenic climate change, such pressures are likely to increase, as human populations, presently about 6.5 billion, are projected to rise to 12.8 billion by 2050 (if fertility remains at present levels).

In human-influenced landscapes, two broad classes of plants are often recognised, based on their apparent success or relative failure. Thus, some species are ‘winners’ (crop plants, weeds, invasive plants etc.). Others, the endangered species, are ‘losers’ or ‘potential losers’, with extinction their likely fate. Put simply, some plant species appear to be at a selective advantage in changing ecosystems and their populations are stable or increasing, while others faced with the same selection pressures are declining and threatened with extinction. Traditionally, but with some honourable exceptions, these two facets of evolutionary change are treated as separate subjects in academic books and elsewhere. Here, the notion of winners and losers is considered as a single concept, as major insights emerge through such an approach.

This chapter considers the microevolutionary implications of creative conservation, which involves habitat restoration and species reintroduction. It considers underlying concepts and practice, including which stocks to use in projects.

Bradshaw (1987) has devised a general model of ecosystem restoration (Fig. 16.1) to take account not only of the aims of conservationists in parks and reserves, but also the schemes of a wide range of professionals, including landscape architects and landscape gardeners, who have undertaken projects for government departments, local authorities, industrial corporations and private landowners etc. Not all these restorations aim to promote wildlife conservation, although they may do so indirectly. Some are/were concerned with restoring damaged areas to productive farmland, removing pollutants from rivers and lakes, restoring watersheds to prevent erosion etc. (Bradshaw & Chadwick, 1980; Jordan, Gilpin & Aber, 1987; Falk, Palmer & Zedler, 2006). Restoration for nature conservation is, therefore, only one strand in the complex relationship of humans to their landscape.

Restoration presents the ecologists with powerful challenges, providing the ‘acid test’ of the ecologist's understanding of vegetation (Bradshaw, 1987). Harper (1987) likens ecological restoration to the repair of a watch: taking it to pieces provides an understanding of how it works and how it might be rebuilt.

Turning to the details of the model, the diagram indicates how human activities have changed natural habitats. Sometimes ecosystems have been severely degraded, and such areas may be rehabilitated towards their original state by natural plant succession.

Conservation efforts aim to prevent the extinction of endangered species and to provide them with a long-term evolutionary future. In 2000, a colloquium of the National Academy of Sciences of the USA, meeting in Irvine, California, considered ‘The biotic crisis and the future of evolution’ (papers given at the meeting were published in Proceedings of the National Academy of Sciences, USA, 98, 2001). Myers and Knoll (2001, 5389), speaking at the meeting, concluded that ‘human activities have brought the Earth to the brink of biotic crisis’ and ‘in decades to come a large number of species will be lost’. This pessimistic assessment was echoed by many others at the colloquium. It is significant, however, that, while several speakers mentioned climate change, they did not highlight it as a major issue. In less than a decade, there have been major advances in our understanding. As we shall see in this chapter, anthropogenic climate change presents a dramatic and potentially catastrophic threat to the world's biodiversity with profound implications for the theory and practice of conservation.

Doubts about modelling

Some naturalists, accustomed to a life outdoors, are antagonistic to the study of ecological/conservation issues through computer modelling, and doubt the value of such studies in the prediction of future trends. However, it is important to accept that modelling provides important helpful insights that cannot be obtained by any other means. While acknowledging the limitations of models with their simplifying assumptions, it would be foolish not to take their conclusions seriously.

There is increasing evidence that climate change is occurring, and the anthropogenic contribution to such change is being clarified (IPCC, 2007a, b, c, d). While most experts in the field accept this proposition, a diminishing number of vocal sceptics are to be found in academia, in political circles and in the media. This chapter considers the evidence for climate change. Chapters 19 and 20 examine the microevolutionary consequences of such changes, and the implications for conservation.

The greenhouse effect and climate change

Solar energy is received on Earth from the Sun. Some of this energy is reflected back from clouds and the Earth's surface, but some is trapped by the so-called greenhouse gases (water vapour, carbon dioxide, carbon monoxide, methane and nitrous oxide) resulting in the warming of the planet. As we shall see, there is mounting evidence that anthropogenic activities are increasing the levels of these gases in the atmosphere resulting in global warming.

This account draws on the recent Fourth Intergovernmental Panel on Climate Change Assessment Report (IPCC, 2007a) on the physical sciences basis for accessing climate change. It has been prepared by over 1,200 expert authors, and reviewers from 40 countries (Giles, 2007). At the time of writing only the Summaries for Policy Makers are available.

In the last chapter the origin, scale and accelerating impact of the rising tide of humanity were reviewed together with an account of the origins of environmentalism, a movement that subjects our increasing exploitation of the Earth's resources to the most critical scrutiny with the hope that human use will become more sustainable. This chapter introduces a number of other concepts and ideas that are helpful in understanding the setting for the contemporary microevolutionary drama.

Cultural landscapes

Humans are social beings and it is recognised by anthropologists, archaeologists and others that different regions of the world have their own characteristic ‘cultural landscapes’, each of which reflects the different civilisation, customs and artistic achievements of the people who produced it and live within it. Today, there is an astonishing array of cultural landscapes ranging from the dwindling lands of the last remaining hunter-gatherers, through the multitude of different agricultural landscapes to the cityscapes and urban industrial landscapes of modern civilisations.

Cultural landscapes first began to evolve as humans migrated to distant parts of the globe as hunter-gatherers, and these were superseded by the landscapes of the settled agriculturist. From these early beginnings, a wide diversity of cultural landscapes has developed. Many of the observable differences relate to the crop plants grown, and current agricultural practices related to the climate, soils etc. of different regions.

A call for parks to preserve forests

Wallace, the co-founder, with Darwin, of the theory of evolution by natural selection, understood the value – and the vulnerability – of the natural world. Writing in 1910, he made an impassioned plea (quoted in Berry, 2002, 147):

The concept of nature reserves has a long history. As we shall see, important advances were made in the nineteenth century, with the development of national parks in North America. Currently, it has been estimated that c. 7.9% of the Earth's land surface and c. 0.5% sea area are protected in reserves of various kinds (Balmford et al., 2002, 952). Ten different types of parks are listed by Given (1994, 96; Table 15.1), ranging over closed reserves, national parks, extractive reserves etc. The establishment of reserves for nature conservation has been one of the most important and ‘enduring strategies for the conservation of global diversity’ (Hopper, 1996, 253).

Earlier chapters have been designed to serve particular purposes. Chapter 3 provides a connected overview of the concepts underlying our current understanding of the long history of plant evolution. Chapter 4 reveals that while on a geological time scale, humankind arrived on the scene relatively recently, human impacts on the Earth's ecosystems have been very dramatic and are destined to increase. Examples of the effects of human activities on ecosystems are all around us, and it could be claimed that such interactions are so obvious they hardly need to be documented. However, as we have seen above, evidence suggests that the cumulative impact of human activities on the biosphere, both directly and at a distance, have often been underestimated. Also, the full complexity of the interactions of plants and humans is becoming evident, resulting in the recognition of many different categories. For the convenience of devising helpful groups, a species may often be classified in different categories according to the circumstances (Chapter 6).

In total, there have been many thousands of published papers of different facets of plant evolution. Some have investigated the early evolution of plants and animals, others have examined the patterns and processes that have generated, through time, the millions of species that live on Earth.

As we celebrate the 200th anniversary of his birth and the 150th anniversary of the publication of On the Origin of Species in 2009, it is interesting to realise that Darwin made predictions about the outcome of a change in climate, a natural event in his speculation, rather than the anthropogenically induced changes we now face (Darwin, 1901, 59):