26.1. Introduction

This chapter assesses literature on observed and projected impacts, vulnerabilities, and risks as well as on adaptation practices and options in three North American countries: Canada, Mexico, and the USA. The North American Arctic region is assessed in Chapter 28: Polar Regions. North America ranges from the tropics to frozen tundra, and contains a diversity of topography, ecosystems, economies, governance structures, and cultures. As a result, risk and vulnerability to climate variability and change differ considerably across the continent depending on geography, scale, hazard, socio-ecological systems, ecosystems, demographic sectors, cultural values, and institutional settings. This chapter seeks to take account of this diversity and complexity as it affects and is projected to affect vulnerabilities, impacts, risks, and adaptation across North America.

No single chapter would be adequate to cover the range and scope of the literature about climate change vulnerabilities, impacts, and adaptations in the three focus countries of this assessment. (Interested readers are encouraged to review these reports: Lemmen et al., 2008; INECC and SEMARNAT, 2012a; NCADAC, 2013.) We therefore attempt to take a more integrative and innovative approach. In addition to describing current and future climatic and socioeconomic trends of relevance to understanding risk and vulnerability in North America (Section 26.2), we contrast climate impacts, vulnerabilities, and adaptations across and within the three countries in the following key sectors: water resources and management(Section 26.3); ecosystems and biodiversity (Section 26.4); agriculture and food security (Section 26.5); human health (Section 26.6); and key economic sectors and services (Section 26.7). We use a comparative and place-based approach to explore the factors and processes associated with differences and commonalities in vulnerability, risk, and adaptation between urban and rural settlements (Section 26.8); and to illustrate and contrast the nuanced challenges and opportunities adaption entails at the city, subnational, and national levels (Sections 26.8.4, 26.9; Box 26-3). We highlight two case studies that cut across sectors, systems, or national boundaries.