Prevention, mitigation and adaptation

Mitigation and adaptation

With very few exceptions (e.g. Gouache et al., 2011), pest risk simulations have not included options that farmers and growers might take to mitigate for, or adapt to, an increased future pest risk. This is true for agriculture (Juroszek and von Tiedemann, 2015) and forestry (Bentz and Jönsson, 2015). Nevertheless, in agriculture there are a range of potential short-term mitigation and adaptation options available and these should be considered, not only by farmers and growers but also for inclusion in simulation models to support future decision-making. Further development of tools required for adaptive management of pests will increase the probability of successful adaptation strategies in the future (Macfayden, McDonald and Hill, 2018).

Improved host-plant resistance (and competitiveness of crop plants to weeds) and adjustments to pesticide application are considered by most scientists to be the two most effective ways of adapting crop protection to future climatic conditions (reviewed by Juroszek and von Tiedemann, 2015). Other options include adjustments to sowing time, longer crop rotation, improved pest forecasting, adjustment of agronomic practices such as irrigation and fertilization, and provision of targeted advice (Juroszek and von Tiedemann, 2015). Interestingly, several other potential adaptation tools in crop protection, such as modification of the microclimate by altering sowing density, are not discussed at all in the literature related to pest risk simulations.

In forestry and agriculture, climate-smart strategies for pest management may also need to be adopted (Heeb, Jenner and Cook, 2019; Lipper et al., 2014). In general, integrated pest management includes a wide range of direct and indirect plant-health management measures (Heeb, Jenner and Cock, 2019; Juroszek and von Tiedemann, 2011). These include quarantine (biosecurity), other phytosanitary measures (e.g. healthy seeds and seedlings), careful monitoring and optimal timing of needed interventions (Heeb, Jenner and Cook, 2019; Strand, 2000) or biological control (Eigenbrode, Davis and Crowder, 2015).

In the context of adapting cropping systems to climate change, breeding for disease resistance is one of the most attractive options (Miedaner and Juroszek, 2021a, 2021b). Varieties with tolerance to drought, high temperatures, and pests are crucial for food security in staple crops such as maize and beans as well as for cash crops for export, such as coffee and soybeans. Sometimes, new varieties allow adjustments in farming systems in order to moderate the pest risk associated with likely changes. For example, the availability of new wheat varieties permits wheat crops in central Queensland (Australia) to be planted three to four weeks earlier (Howden, Gifford and Meinke, 2010). Also, in the case of cocoa, a multi-criteria selection in developing new varieties is suggested in the context of climate change (Cilas and Bastide, 2020). Although crop breeding, and especially tree breeding, has a long lag time in response to new challenges, models of climate-change effects on pest risk can help to inform strategies in advance of new problems. The identification, conservation and use of ancient varieties can also be useful.

In forestry, adaption to respond to potential climate-change effects is most likely to involve preventive measures, such as removing infested trees to avoid further spread of pests, because of the difficulties in effectively managing tall adult trees (Bonello et al., 2020; Liebhold and Kean, 2019). Another major preventive adaptation option is the exploitation of genetic diversity: the choice of suitable tree species, or pest-resistant or tolerant clones or cultivars if available, when new forests are planted (Bonello et al., 2020).

The choice of adaptation strategies will depend on many factors. Cost is one factor, with Srivastava, Kumar and Aggarwal (2010) concluding that more low-cost adaptation strategies, such as changing the sowing date and choice of cultivar, should be explored to reduce the vulnerability of crop production to climate change. The practicality of changing planting or harvesting dates, however, is dependent on the potential yield penalty and on the location where the crop is grown, the cultivar preferences of farmers and consumers, and the market situation (Wolfe et al., 2008). More expensive adaptation options may also be needed (Juroszek and von Tiedemann, 2011). This may involve, for instance, the development of more powerful methods to manage pathogens in crop residues, which could be combined with already well-established methods such as crop rotation in order to avoid saprophytic colonization of crop residues by pathogens and to decrease the carry-over of inoculum between cropping seasons (Melloy et al., 2010). “Old-fashioned” methods such as turning the soil can also be a powerful way to manage diseased crop residues (Miedaner and Juroszek, 2021b), although conservation agriculture might be better suited in drought-prone areas. Ploughing the soil also entails more fuel input and hence more climate-relevant CO2 emissions compared to minimum tillage.

Finally, considering strategic planning, it is important to decide where to grow perennial agricultural crops such as date palms (Shabani and Kumar, 2013). With knowledge about where economically important crop diseases of such crops might occur in the future, low-risk locations could be identified in order to avoid or minimize the future impact of these diseases (Shabani and Kumar, 2013). This applies also to forestry, where planning is particularly important to avoid or minimize future increasing pest risks, as explained above. For annual crops such as oilseed rape, shifting of cultivation zones has been suggested as one of the adaptations under a worse-case scenario (Butterworth et al., 2010). Indeed, in Egypt, faba bean cultivation has been shifted from central Egypt to the cooler Nile Delta region in the north to escape the detrimental impacts of viral disease, possibly caused – at least in part – by global warming.

All of the options highlighted above may have a role to play in allowing farmers and growers to mitigate for, and adapt to, an increased pest risk. In general, however, it will be important to favour and implement those technologies and practices that are able to simultaneously contribute to increased productivity and reduced vulnerability to the changes brought about by climate-relevant emissions including CO2, N2O and CH4.