**3. Human impact on plant genetic resources and options for their maintenance**

There is rising awareness that habitat loss is associated with loss of genetic diversity; however the basic cause-effect relationships underlying the ecological roles of biodiversity are still poorly understood [22]. Major tropical wilderness areas show strong coincidence of biodiver‐ sity, people and concerns over watershed functions and are in a state of decrease or degrada‐ tion as natural forests are converted into other land use classes and little area transforms back to natural forests or is reforested with plantations [23]. Various drivers are important for that. There is a high negative correlation of population density on species richness and tree diversity for tropical rainforests [24] but neither population nor poverty is the sole and major reason for land use and land cover change. It is driven by people's reaction to economic opportunities and constraints, created by local as well as national markets and policies. Additionally, global forces become main determinants as they intensify or weaken local factors [25].

Sustainability in agriculture suggests a focus on both improved understanding of the benefits of ecological and agronomic management, manipulation and redesign, and genotype im‐ provements through the full range of modern biological approaches. A sustainable manage‐ ment of agro-ecosystems which includes aspects such as energy flows, nutrient cycling, human impacts and resilience may enhance reshaping of agriculture in landscapes. Sustainable cropping systems will influence food production, pesticide use and carbon stocks in a positive way. But the development of national and international policies supporting a stronger expansion of such systems in developed as well as developing countries still remains a major challenge [26]. Key drivers in the decline of biodiversity, its conservation and ecosystem services are the increased use of pesticides, herbicides and fertilizers, an increased homoge‐ neity of landscapes associated with regional and farm-level specialization, drainage of water logged fields, loss of marginal and un-cropped habitat patches, and reduced fallow periods. Additionally, the intensification of agriculture has been fundamental to the degradation of ecosystem services and increases both, the production of greenhouse gases and a reduction of carbon sequestration [27].

Looking at the human impact on the earth system, nine planetary boundaries can be defined whereby the transgression of one or more of them is considered harmful due to abrupt environmental changes within continental- to planetary-scale systems. Three of them - climate change, the global nitrogen cycle and the rate of biodiversity loss - have already surpassed their threshold levels leading to consequences for global sustainability [28]. Strong negative impacts upon ecosystems are expected when the increasing annual global mean temperature rises above the pre-industrial mean by 2°C or more, especially in biodiversity hotspots [29].

The supply of non-timber forest products, timber and other services by forests resume a safety net function for rural populations providing both, income and jobs. Hence, fostering the role of forests in the political debate is essential, not only when looking at mitigation and adaption strategies for climate change but also for achieving sustainable developmental goals [30]. Experiences from Central Africa involving a wide range of stakeholders showed that focused research on priority sectors for poverty reduction are likely to raise public awareness of the forests' role and contribution to mitigate and to adapt to climate change at regional and national levels. A key for improving coherence and effectiveness of forest management policies is establishing the link between forests and climate change adaptation [30].

Plant genetic resources are essential for farmers to cope with future challenges, a feature emphasized by the FAO Commission on Genetic Resources for Food and Agriculture. New within-crop diversity will be needed to adapt to future conditions, and even new crops will be required under extreme conditions to reduce risks induced by climate change [4].

Despite progress in the past, crop wild relatives and underused species for food and agriculture need to be secured. The need for adapted germplasm is urgent and requires characterization, evaluation, and the availability of materials but gaps in *ex-situ* collections of selected crop gene pools are huge. The current focus on major crops leads to concerns due to a lack of *in-situ* and on-farm conservation. This neglects the importance of genetic, species, and ecosystems diversity. Currently, six million plant accessions are conserved in gene banks worldwide, representing a very limited number of species. Half of them are improved cultivars or breeders' lines. Only one third, however, represents landraces or old cultivars. About 15% refer to wild relatives of crop species and weeds. Minor crops and underutilized species are largely underrepresented in these collections, particularly primitive cultivars and wild relatives from the centres of origin's diversity and cultivation. Another obstacle is that only a third of all gene bank accessions have been fully characterized [1].

However, for many other crops, especially neglected or underutilized species and wild relatives of crops, comprehensive collections still do not exist and considerable gaps remain to be filled. There is also need for a better communication, collaboration and partnerships among institutions dealing with the management of plant genetic resources, from conservation to plant breeding and seed systems [4].

services are the increased use of pesticides, herbicides and fertilizers, an increased homoge‐ neity of landscapes associated with regional and farm-level specialization, drainage of water logged fields, loss of marginal and un-cropped habitat patches, and reduced fallow periods. Additionally, the intensification of agriculture has been fundamental to the degradation of ecosystem services and increases both, the production of greenhouse gases and a reduction of

Looking at the human impact on the earth system, nine planetary boundaries can be defined whereby the transgression of one or more of them is considered harmful due to abrupt environmental changes within continental- to planetary-scale systems. Three of them - climate change, the global nitrogen cycle and the rate of biodiversity loss - have already surpassed their threshold levels leading to consequences for global sustainability [28]. Strong negative impacts upon ecosystems are expected when the increasing annual global mean temperature rises above the pre-industrial mean by 2°C or more, especially in biodiversity hotspots [29].

The supply of non-timber forest products, timber and other services by forests resume a safety net function for rural populations providing both, income and jobs. Hence, fostering the role of forests in the political debate is essential, not only when looking at mitigation and adaption strategies for climate change but also for achieving sustainable developmental goals [30]. Experiences from Central Africa involving a wide range of stakeholders showed that focused research on priority sectors for poverty reduction are likely to raise public awareness of the forests' role and contribution to mitigate and to adapt to climate change at regional and national levels. A key for improving coherence and effectiveness of forest management policies is

Plant genetic resources are essential for farmers to cope with future challenges, a feature emphasized by the FAO Commission on Genetic Resources for Food and Agriculture. New within-crop diversity will be needed to adapt to future conditions, and even new crops will

Despite progress in the past, crop wild relatives and underused species for food and agriculture need to be secured. The need for adapted germplasm is urgent and requires characterization, evaluation, and the availability of materials but gaps in *ex-situ* collections of selected crop gene pools are huge. The current focus on major crops leads to concerns due to a lack of *in-situ* and on-farm conservation. This neglects the importance of genetic, species, and ecosystems diversity. Currently, six million plant accessions are conserved in gene banks worldwide, representing a very limited number of species. Half of them are improved cultivars or breeders' lines. Only one third, however, represents landraces or old cultivars. About 15% refer to wild relatives of crop species and weeds. Minor crops and underutilized species are largely underrepresented in these collections, particularly primitive cultivars and wild relatives from the centres of origin's diversity and cultivation. Another obstacle is that only a third of all gene

However, for many other crops, especially neglected or underutilized species and wild relatives of crops, comprehensive collections still do not exist and considerable gaps remain to be filled. There is also need for a better communication, collaboration and partnerships

be required under extreme conditions to reduce risks induced by climate change [4].

establishing the link between forests and climate change adaptation [30].

bank accessions have been fully characterized [1].

carbon sequestration [27].

128 Agroecology

Since farmers know best which materials meet their needs and are enthusiastic seekers of new varieties, "participatory plant breeding" represents a promising approach to enhancing agrobiodiversity [3]. Their participation in the whole process from the selection of plant genetic material up to development of cropping systems would improve and help to meet their needs, while also sustaining food security and alleviating poverty. Plant breeding of major crops, however, often lacks this participation, neglecting marginal site conditions and fostering high input demanding improved varieties.

Genetic diversity is essential for improving crops already in use but also for developing potential novel crops. The successful use of plant genetic resources and their sustained production depend to a large degree on access to genetically diverse germplasm. Free international exchange of germplasm will contribute significantly to the worldwide develop‐ ment of new industrial crops [31]. This is another challenge which needs to be solved in an equitable and fair way. Often indigenous knowledge is highly esteemed by people but once it comes to payment for such services people are reluctant to do so. Contracts for compensating creativity of farmers and a framework for rewarding grass root creativity and innovation are possible solutions [32], while consumers' and traders' responsibility is fostering fair trade, supporting local people in their production of food, feed, fibre and fuel [33]. Four types of collaboration are considered vital for using plant genetic resources in a sustainable way: (i) a national regulatory framework for biodiversity prospecting, (ii) the development of infra‐ structure and technology; (iii) formal contractual relationships among biodiversity's sources, intermediaries and final users; and (iv) the moving of research and development into the source country so as to contribute to its gross national product [16].

There are knowledge gaps with regard to the world's ability to match both a bio-based energy production and maintaining food security at the same time [34]. The main challenge is the competition for arable land and limited fresh water resources associated with a fast growing demand for food, feed, fibre, and fuel worldwide. A solution requires higher crop yields and improving resource-use efficiencies, especially that of nitrogen, and water productivity in production systems over the next two or three decades which is only possible with high external inputs. Cropping systems adapted to climate change and improved stress tolerance of crops are key issues in this context. This can be achieved by genetic improvement of crops and establishing sustainable cropping systems in diverse environments. Integrated assess‐ ments of their impact on resources, environments, and people's welfare can help identifying management options, species and varieties well adopted or most appropriate for specific environments. This will largely depend on the added value regarding specific ambitions, i.e. food, feed, fibre or fuel [34].

Energy wealth in Latin America has so far contributed little to overcome poverty and foster development. The sometimes considerable oil and gas earnings are not used to improve general welfare but skimmed off by the elite. A major problem is that both, energy reserves and energy utilization, are unevenly distributed in Latin America [35]. Using bioenergy is an option for an improved participation of rural communities if political leaders set the right frame.

There is lack of proper research, training, and socio-economic information to produce biofuels in a sustainable way. Hence, research in agriculture has to set a focus on improved crop selection based on the local situation and on management options including cultivation, management of pests and diseases, mechanisation, and harvesting. Furthermore, it is neces‐ sary to adapt cropping systems to local soil conditions and use by-products of biofuel crops to increase the efficiency of nutrient use and decrease negative influences on the environment. This is essential for the sustainable production of bio-fuel crops [36].

There are two main approaches to conserve plant genetic resources:


Both approaches can also be applied to conserve agro-biodiversity where many land-races have vanished since the green revolution in the 1960ies. However, effectively conserving wild biodiversity in agricultural landscapes will require increased research, policy coordination, and strategic support to agricultural communities and conservationists [38]. Research needs to address open questions regarding the minimum size and level of area connectivity required to conserve biodiversity *in-situ* at landscape level. *Ex-situ* conservation is biased by human decisions. But where shall we set priorities for sampling? Who pays for the costs of collecting and sustaining such kind of environmental services? Can value be added by exploring options for development of bio-products? Identifying common priorities in shared natural resource systems, however, is a major step in sharing a common responsibility in addressing climate change and associated problems.
