This review paper is based on the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change, in particular on the Working Group I (WG I) ‘The physical science basis’ and on the WG II ‘Impacts adaptation and vulnerability’ reports. The WG I report represents the state of the current scientific understanding of the observed and projected climate changes. The natural and anthropogenic drivers of climate change are addressed, focusing on the physical science understanding of observed records and on model-generated global climate change scenarios. The WG II report concerns the relationship between the observed changes of climate variables and the changes in the natural and human environment, addressing key policy-relevant scientific findings. Projected impacts and findings about vulnerability and adaptation on fresh water, natural ecosystems, food, fiber, coastal areas industry and health are also addressed for all continents. Scientific findings subsequent to the publication of the AR4 are not included in this review paper, whereas the recent decisions by the European Union (EU) and the agreements adopted within the United Nation Framework Convention on Climate Change based on the AR4 are reported.

The livestock sector has a key and growing role in the agricultural economy. It is a major provider of livelihood support for a large part of the world's poor. It is also an important determinant of human health and diet. Over the last three decades, the global livestock sector has rapidly evolved in response to human population growth, income growth and urbanization. And until recently, much of the focus of the sector has been geared towards satiating this demand. However, the rapid growth in demand for animal protein, has resulted in complex interactions among bio-physical resources, economic and social objectives with implications for the natural resource-base and the environment. Livestock production has a large impact on the world's natural resources and contributes significantly to environmental problems such as ecosystem pollution and degradation, global warming and climate change by emission of greenhouse gases and biodiversity loss. This paper provides an overview of the growth within the livestock sector, explores the inter-linkages between the rapidly increasing demand for animal protein and environmental consequences, as well as advances possible technical and policy interventions that are appropriate for the enhancement of the sector's role in food security, poverty reduction, economic development while contributing to environmental sustainability.