We explore the issues relevant to those types of ecosystems containing new combinations of species that arise through human action, environmental change, and the impacts of the deliberate and inadvertent introduction of species from other regions. Novel ecosystems (also termed 'emerging ecosystems') result when species occur in combinations and relative abundances that have not occurred previously within a given biome. Key characteristics are novelty, in the form of new species combinations and the potential for changes in ecosystem functioning, and human agency, in that these ecosystems are the result of deliberate or inadvertent human action. As more of the Earth becomes transformed by human actions, novel ecosystems increase in importance, but are relatively little studied. Either the degradation or invasion of native or 'wild' ecosystems or the abandonment of intensively managed systems can result in the formation of these novel systems. Important considerations are whether these new systems are persistent and what values they may have. It is likely that it may be very difficult or costly to return such systems to their previous state, and hence consideration needs to be given to developing appropriate management goals and approaches.

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The management of landscapes for biological conservation and ecologically sustainable natural resource use are crucial global issues. Research for over two decades has resulted in a large literature, yet there is little consensus on the applicability or even the existence of general principles or broad considerations that could guide landscape conservation. We assess six major themes in the ecology and conservation of landscapes. We identify 13 important issues that need to be considered in developing approaches to landscape conservation. They include recognizing the importance of landscape mosaics (including the integration of terrestrial and aquatic areas), recognizing interactions between vegetation cover and vegetation configuration, using an appropriate landscape conceptual model, maintaining the capacity to recover from disturbance and managing landscapes in an adaptive framework. These considerations are influenced by landscape context, species assemblages and management goals and do not translate directly into on-the-ground management guidelines but they should be recognized by researchers and resource managers when developing guidelines for specific cases. Two crucial overarching issues are: (i) a clearly articulated vision for landscape conservation and (ii) quantifiable objectives that offer unambiguous signposts for measuring progress.

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Summary1. Native recolonization of abandoned farmland in the wheat-growing region of western Australia is slow to non-existent, even 45 years after abandonment. Instead, old-fields tend to be dominated by non-native annual grasses. The native vegetation in the region is highly fragmented. We predicted that recovery is limited by seed availability and recruitment failure. 2. We compared the seed rain, soil seed bank and extant vegetation of three old-fields and three adjacent native woodland remnants to test our predictions. 3. Seed dispersal limitation was evident at two old-fields: species richness of the native seed in the soil seed bank declined at 50-m increments (i.e. 0 m, 50 m and 100 m) into the old-fields. Species richness of recolonizing native vegetation also declined along this transect. 4. Recruitment limitation was evident at one old-field, probably linked to the few abundant non-native species that dominated the vegetation. These non-natives dominated the seed supply, and tended to germinate more rapidly than the native seeds. 5. In contrast, seed dispersal and recruitment had not limited native recolonization of the third old-field: 91% of the species present in the adjacent remnant had recolonized this old-field. Species richness and abundance of non-natives in the seed supply and extant vegetation were minor compared with that of the other old-fields. Therefore an adequate seed supply of natives, the lack of non-natives and chance natural disturbance events (i.e. cyclone and fire) had probably contributed to this result. 6. Synthesis and applications. Native recolonization of wheatbelt old-fields is contingent upon the unusual coincidence of seed availability, favourable conditions for recruitment and an absence of competitive non-natives. Grasses, annual herbs and Acacia shrubs are dominant among the few native species that have consistently recolonized these oldfields. In most cases, direct seeding and control of non-natives are the minimum requirements for restoration of wheatbelt old-fields to species-rich eucalypt woodlands.