Climate change and tree genetic resource management: maintaining and enhancing the productivity and value of smallholder tropical agroforestry landscapes. A review

Abstract

Anthropogenic climate change has significant consequences for the sustainability and productivity of agroforestry ecosystems upon which millions of smallholders in the tropics depend and that provide valuable global services. We here consider the current state of knowledge of the impacts of climate change on tree genetic resources and implications for action in a smallholder setting. Required measures to respond to change include: (1) the facilitated translocation of environmentally-matched germplasm across appropriate geographic scales, (2) the elevation of effective population sizes of tree stands through the promotion of pollinators and other farm management interventions; and (3) the use of a wider range of 'plastic' species and populations for planting. Key bottlenecks to response that are discussed here include limitations in the international exchange of tree seed and seedlings, and the absence of wellfunctioning delivery systems to provide smallholders with better-adapted planting material. Greater research on population-level environmental responses in indigenous tree species is important, and more studies of animal pollinators in farm landscapes are required. The development of well-functioning markets for new products that farmers can grow in order to mitigate and adapt to anthropogenic climate change must also consider genetic resource issues, as we describe.

Exotic tree species displace indigenous ones on farms at intermediate altitudes around Mount Kenya

“…Farmers may simply not find quality planting material of the few exotic tree species suitable for drylands such as mangoes close to their farms. On the other hand, some of these 'generalist' exotic species may contribute to adaptation of farming systems to climate change (Dawson et al 2011). Results of this study shown in Table 7 zones, but also several of the indigenous trees, e.g.…”

“…One example is the poor performance of Rwandan Grevillea robusta provenances as compared to wild Australian ones (Kalinganire and Hall 1993), another the invasion of the cypress aphid Cinara cupressivora and the woolly adelgid Pineus boerneri in exotic conifer plantations in eastern and southern Africa (Day et al 2003). Greater tree diversity including 'plastic' indigenous tree species buffers farming systems against the mentioned challenges, which is of particular importance in the face of climate change (Dawson et al 2011). Indigenous tree species have highest priority for conservation to prevent their extinction in their threatened natural habitat (Dawson et al 2009).…”

Morphological variation in Balanites aegyptiaca fruits and seeds within and among parkland agroforests in eastern Niger

“…Although the species can regenerate vegetatively from sucker shoots, natural regeneration from genetically diverse seed pools is essential to facilitated adaptation to environmental change, and in particular to projected climate change in the region (Dawson et al 2010). It is important, therefore, that tree domestication programs work in a participatory manner with rural communities to develop sustainable production and harvesting plans and long-term conservation plans to safeguard the genetic resources of this species.…”

Restoring forests: What constitutes success in the twenty-first century?

“…Research is needed, for example, to improve selection of better-adapted seed sources for outplanting in different environmental conditions; this is particularly crucial for native species in semi-arid zones that will become increasingly hotter and drier in the future (Weber and Sotelo Montes 2010;Weber et al 2015). Intense debate has been raised at multiple levels regarding some applications of genetics to forest restoration, i.e., assisted migration of provenances and species (Dawson et al 2011;Williams and Dumroese 2013;Stanturf et al 2014) or the use of classical breeding versus genetic engineering (Merkle et al 2007;Jacobs et al 2013; Fig. 3), suggesting that we are in the infancy of navigating these dynamic and critical issues that have long-lasting consequences toward success of forest restoration programs.…”