**1. Introduction**

Since the dawn of mankind people explore the cornucopia of the plant kingdom to obtain food, feed, fiber, and fuel. Worldwide, the total number of higher plants is estimated to be 270,000 species. About 43% of them are crops, cultivated plants, and their wild relatives, nowadays being classified as plant genetic resources for food and agriculture. Throughout the history only 7000 species representing almost 2.5% of the total were cultivated by mankind in the one or other way [1].

Mankind has largely benefited from modern agriculture. Today, agriculture provides food, feed, fuel, and fiber for more than 7,000 million people whereas a hunter-gatherer lifestyle supported around 4 million people only. In the past four decades, global cereal production almost doubled. This strong increase was based on greater use of inputs such as fertilizer, water, pesticides, new crop varieties, and other technologies provided by the 'Green Revolu‐ tion'. This helped to diminish hunger, improve nutrition, and spare natural ecosystems from conversion to cropland. By 2050, the population is expected to have increased by 50%. Increasing and sustaining food production for a growing world population will, therefore, be a major challenge in future; however achieving this without compromising environmental integrity and public health is even more challenging due to changing habits in food consump‐ tion in parts of the world, a rising demand for biofuel, diminishing returns to fertilizer, and an increasing water demand [2].

Although new crop varieties substantially contributed to increase crop yields, specialized plant breeding has led to a strong dependence on few crops only along with erosion of plant genetic

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resources. For thousands of years farmers have been domesticating plant species thereby developing a wide range of crop varieties adapted to specific needs and environmental conditions [3]. Over the past 100 years the importance of many crop species has decreased strongly and many adapted crop varieties diminished. The private agricultural sector in‐ creased significantly in both developed and developing countries during the past 20 years; however, the main focus of its interest has been high-value products, such as maize, wheat, rice, oil crops, pulse crops and vegetable crops [4]. Today, 30 crops provide 95% of human food energy needs, 12 crops together with five animal species deliver 75 % of the world's food today, and three of which, i.e. rice, wheat, and maize, are responsible for more than 60% of our energy intake [5]. Almost 90% of global vegetable oil is produced by four crops only; i.e. oil palm, soybean, oil seed rape and sunflower [6]. Nowadays, our food security depends on a tiny number of crops only; it is therefore essential to sustain a high genetic crop diversity for both coping with increasing environmental stresses and facilitating farmers and researchers with options to breed cultivars adapted to less favourable conditions, such as salinity, poor soils and extreme weather events and that can resist biotic stresses, such as pests and diseases [4].

Many studies and reports discuss the importance of plant genetic resources for crop production in view of climate change and their key role in adapting to adverse climatic conditions and, hence, for food security. Important is that underutilized or minor crops often harbour high levels of genetic diversity being maintained on-farm in small-scale farming systems; however they are relatively neglected by formal research and development strategies, including breeding programs. Results from Peru hosting a wealth of native agro-biodiversity including many underutilized crops indicated the potential of a breeding approach for indigenous Andean crops, based on a combination of evolutionary and participatory methods to reach a balance between yield improvement and maintenance of genetic diversity [7]. These authors also highlighted the importance for upscaling such activities but mentioned the need to address methodological, financial and institutional issues for further expansion. Such activities are particularly important for areas threatened by climate change and to safeguard local food production. A global analysis of climate risks for crops in 12 food-insecure regions indicated South Asia and Southern Africa as two regions that, without sufficient adaptation measures, are likely to suffer from negative impacts on several crops important to large food-insecure human populations [8]. Therefore, these areas need special attention in crop development and breeding for food security based on local seed systems.

Minor crops can be important at a local, regional and national level but are often neglected at an international level. They are staple foods, contributing to food supply in certain periods and to a nutritionally well-balanced diet but also supply raw materials such as oils, fibres and dyes, providing options for income generation. Plant genetic resources are sometimes also well adapted to marginal soil conditions, an important feature in face of climate change and increasing soil degradation in densely populated regions. Minor crops are neglected as their advantages are known only locally and due to lack of markets, infrastructure for processing, and international research activities. Their potential, however, is often only poorly addressed and the loss of plant genetic resources reduces current and future options for mitigation in the agricultural sector [3].

On this background, this chapter intends to reflect the importance of plant genetic resources for people's livelihood and the human impact on plant genetic resources in general, looks at opportunities how the use of genetic resources and introduction of new or minor crops can contribute to improve people's livelihood and discusses tools for impact assessment.
