Observed Impacts of Global Climate Change in the U.S.

Foreword ii

Executive Summary iii

I. Introduction 1

A. Overview 1
B. Global Climate Change Patterns 3
C. Biological Responses to 20th Century Global Warming 5

II. Potential Effects of Climate Change on Wild Plants, Animals,
and Ecological Processes 6

A. Evolutionary Changes 7
B. Physical and Physiological Changes 7
C. Phenological Changes 8
D. Range Shifts 9
E. Community Changes 9
F. Ecosystem Process Changes 9
G. Complications of Multiple Stressors 10

III. Scope of Review and Evaluation Criteria for Studies 11

IV. Current Observed Climate Change Impacts 13
A. Globally Coherent Signals of Climate Change Impacts 15
B. Observed Changes in the United States 17

IV. Current Observed Climate Change Impacts 13

A. Globally Coherent Signals of Climate Change Impacts 15
B. Observed Changes in the United States 17

V. Strength of Evidence that Climate Change is Already Affecting
Natural Systems 35

VI. Ecological Implications 38

A. Is There Reason for Concern? 38
B. General Recommendations for Conservation 41

VII. Conclusions 43

References 47