Global change (climate change together with other worldwide anthropogenic processes such as increasing trade, air pollution and urbanization) will affect plant health at the genetic, individual, population and landscape level. Direct effects include ecosystem stress due to natural resources shortage or imbalance. Indirect effects include (i) an increased frequency of natural detrimental phenomena, (ii) an increased pressure due to already present pests and diseases, (iii) the introduction of new invasive species either as a result of an improved suitability of the climatic conditions or as a result of increased trade, and (iv) the human response to global change. In this review, we provide an overview of recent studies on terrestrial plant health in the presence of global change factors. We summarize the links between climate change and some key issues in plant health, including tree mortality, changes in wildfire regimes, biological invasions and the role of genetic diversity for ecosystem resilience. Prediction and management of global change effects are complicated by interactions between globalization, climate and invasive plants and/or pathogens. We summarize practical guidelines for landscape management and draw general conclusions from an expanding body of literature.

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Salmon aquaculture in Scotland continues to increase; however, one of the potential limitations to its further sustainable growth is the ectoparasitic sea louse Lepeophtheirus salmonis. The industry in Scotland undertakes coordinated management procedures to control the levels of sea lice on farms in designated production areas. We developed a biophysical sea lice dispersal model for Loch Linnhe, one of the largest fjords on the west coast of Scotland, to provide further information to help establish more effective farm management areas. We successfully extend modelling principles previously applied to a small Scottish fjordic system. Modelling scenarios demonstrate heterogeneity in the distribution of sea lice within the system and simulations, suggesting that lice could be transmitted up to 30 km. The scenarios are assessed by comparing model predictions against lice sampled by both planktonic trawls and settlement on sentinel caged fish. The model predicts the ranked abundance of both planktonic and settled lice assuming that the lice input to the system is relative to host biomass. Data collection is ongoing for undertaking and assessing additional scenarios.

Global aquaculture production continues to increase across a variety of sectors, including Atlantic salmon production in Scotland. One limitation to the expansion of open-cage aquaculture is disease-induced stock losses as well as the potential for disease agents from farms interacting with other farms and possibly with wild salmonids. Epidemiological studies of diseaseagent transmission often omit environmental transmission of organisms, although this process is an integral part of parasite spread and incidence. Within the aquatic environment, water movements enable pathogens and parasites to potentially be transmitted over long distances. As pathogens and parasites are transported, their status can change; they can degrade or, in the case of sea lice, develop into an infectious stage. A combination of biological and physical models is required to understand the transmission of disease-causing organisms. Here we propose a set of components that have been implemented in a range of modelling studies of sea lice dispersal, and describe how such attributes have been used in developing a study in one of Scotland's largest fjordic systems. By developing descriptive simulation model frameworks, which are validated using physical and biological observations, alternative methods of integrated pest management can be investigated and developed. The identification of dispersal routes of sea lice and establishment of potential farm−farm connections can inform sea lice management.

In the majority of salmon farming countries, production occurs in zones where practices are coordinated to manage disease agents such as Lepeophtheirus salmonis. To inform the structure of zones in specific systems, models have been developed accounting for parasite biology and system hydrodynamics. These models provide individual system farm relationships, and as such, it may be beneficial to produce more generalized principles for informing structures. Here, we use six different forcing scenarios to provide simulations from a previously described model of the Loch Linnhe system, Scotland, to assess the maximum dispersal distance of lice particles released from 12 sites transported over 19 day. Results indicate that the median distance travelled is 6.1 km from release site with <2.5% transported beyond 15 km, which occurs from particles originating from half of the release sites, with an absolute simulated distance of 36 km observed. This provides information suggesting that the disease management areas developed for infectious salmon anaemia control may also have properties appropriate for salmon lice management in Scottish coastal waters. Additionally, general numerical descriptors of the simulated relative lice abundance reduction with increased distance from release location are proposed.