Domestication, utilization and conservation of superior agroforestry trees

Tropical agroforestry systems are characterized by great diversity among and within tree species that are found in contrasting biological, complex niches in a spectrum from managed natural forest to intensive farmland production. Different species and production systems have immense value to rural communities that are tree dependent (on both trees in forest and/or in farmland) and to local, national and international markets, and provide wider global services. The diversity of species present and their unique biological characteristics, and the wide range of landscapes (almost natural to completely cultivated) in which tree species are found,  pose major challenges in developing generic models and principles for managing tree genetic resources in effective ways. The lack of quality germplasm, inappropriate farm management practices and a lack of market integration mean that much potential for improving livelihoods and the environment remains untapped. In particular, valuable opportunities to improve the livelihoods of communities are being lost due to:

1. Threats to natural and planted populations of tree stands, with inadequate integration of trees into sustainable farming practices;
2. Those trees species that are integrated in agricultural landscapes are under-performing due to inadequate approaches for silvicultural/horticultural and genetic management;
3. Under investment in the improvement, prioritisation, domestication and wider cultivation of more high value tree species.

The World Agroforestry Centre is addressing these issues in the context of a range of global challenges to production,  including climate change, continued deforestation, further land degradation, increased crop intensification, high levels of ‘hidden hunger’, increases in domestic and international trade, the widening of biotechnology applications to underutilised species, and demographic changes and urbanisation. To promote sustainable and productive agroforestry practices in a range of farming landscapes, research is being focused on the following key problems:

• Limited genetic improvement programmes for smallholder tree species  and a scarcity of tools and practices for on-farm propagation and management;
• Absence of the minimum populations that are necessary for  viable intergenerational sustainability of production for many tree species in farmland;
• Over-centralization of tree seed and seedling supply nationally and the scarcity of information for farmers and other stakeholders on the availability, management and use of agroforestry tree species;
• Scarcity of well-documented, characterised and comprehensive tree germplasm collections for domestication and conservation of species, and for an understanding of negative environmental potentials such as invasiveness behaviour;
• Inadequate national and international policies and efforts to address the utilisation, management and conservation of agroforestry tree germplasm.

The genetic makeup of a tree interacts with environment and management practices over its lifespan to determine growth, productivity and quality for human use. Trees on farm are in various stages of ‘domestication’ as they are retained after spontaneous establishment, are grafted with selected shoots and are planted as seed from unselected or improved germplasm. Different management practices influence genetic resources in various ways at farm, landscape and, ultimately, global levels. Low awareness of ‘quality’ attributes and poor accessibility to ‘good quality’  planting material jointly characterise  the current tree planting practices of smallholders in tropical agroforestry systems, and landscapes thus fall short in their potential to provide goods and services.  On the other hand, current practices sometimes retain high diversity among and within tree species that are found in contrasting niches, promoting a degree of flexibility to external change by improving risk management through resilience. Rather than a one-size-fits-all approach, the needs to improve the productivity of individual species, and at the same time to maintain genetic and species diversity in agroforestry landscapes, require that a range of approaches is adopted for supplying and using tree germplasm effectively in farmland. In understanding current practices and systems and exploring future potentials through research, ICRAF aims to provide practical, direct approaches to increase the immediate and medium-term value of trees in farmland, while conserving the broad pool of tree genetic resources that is needed to ensure sustainability of practices in the long-term.

Tree domestication involves social processes of control in the use and overuse of wild, incipient- and semi-domesticates of tree populations and of the land on which trees are found naturally and in which they can be planted. Human control is exerted over the reproductive cycles of trees and in the production, selection and use of seed and vegetative propagules. In the later stages of domestication, explicit steps of genetic improvement based on specified ‘ideotypes’ dominate, steps which however depend on gene pools collected during incipient domestication. Advanced and early processes of domestication are therefore not independent even though they are based on different strategies.  Many annual food crops have been so extensively bred that further advances in production require sophisticated breeding approaches. In contrast, the almost wild nature of many tree species that are used in agroforestry systems means that there is potential for huge genetic gains with simple improvement strategies. At the same time, genetic resources of many tree species are eroding rapidly both in remnant natural forests and in farmland. With so much untapped variation and the risk of its rapid loss, there is a need for a much better understanding of current drivers of tree domestication, and how to enhance processes of circa situ conservation and local, farmer-based genetic improvement.