Timing of critical biological events, such as spring bud burst, emergence from overwintering, and the start of migrations, has shifted, leading to important impacts on species and habitats.

This finding is from chapter 8 of Climate Change Impacts in the United States: The Third National Climate Assessment.

Process for developing key messages: The key messages and supporting chapter text summarize extensive evidence documented in the Ecosystems Technical Input Report, Impacts of Climate Change on Biodiversity, Ecosystems, and Ecosystem Services: Technical Input to the 2013 National Climate Assessment.7406884d-2302-4644-aa50-12ed8baf4fd7 This foundational report evolved from a technical workshop held at the Gordon and Betty Moore Foundation in Palo Alto, CA, in January 2012 and attended by approximately 65 scientists. Technical inputs (127) on a wide range of topics related to ecosystems were also received and reviewed as part of the Federal Register Notice solicitation for public input.

Description of evidence base: The key message and supporting text summarizes extensive evidence documented in the Ecosystems Technical Input, Phenology as a bio-indicator of climate change impacts on people and ecosystems: Towards an integrated national assessment approach.13f67e66-80b2-4732-992a-1f4fd1e91d03 An additional 127 input reports, on a wide range of topics related to ecosystems, were also received and reviewed as part of the Federal Register Notice solicitation for public input. Many studies have documented an advance in springtime phenological events of species in response to climate warming. For example, long-term observations of lilac flowering indicate that the onset of spring has advanced one day earlier per decade across the northern hemisphere in response to increased winter and spring temperatures, and by 1.5 days per decade earlier in the western United States.655d6652-08ae-4f55-960d-f06297e9eb9e 56447233-ad64-46b3-8371-925de98e78c0 Other multi-decadal studies for plant species have documented similar trends for early flowering.a454cc19-a815-4db9-b074-bb97cb5925fb 5bb98e9a-bb4f-4653-9ad2-8a34477a67dd bab55be2-dd1f-4525-aaa0-b7c1f3c975f4 a7b4b70b-7218-483a-8c77-2f593629fa96 Evidence suggests that insect emergence from overwintering may become out of sync with pollen sources,241f3e50-9b98-464f-b6a7-dc0b6ee243a1 and that the beginning of bird and fish migrations are shifting.f5e7f46d-c229-4474-b70b-6f9478134320 d5af6e55-d90e-4258-b455-c95fc6c9994c eeb20593-b221-4b48-9da2-eae062a14757 7fb94ff1-3d43-4aac-8c66-97633790422b f8043f85-6a17-419e-bd3c-60b4bfdc2a9a 699a7dbf-7a48-439f-8272-b1daf9bad9b1

New information and remaining uncertainties: In addition to the Ecosystems Technical Input13f67e66-80b2-4732-992a-1f4fd1e91d03 many new studies have been conducted since the previous National Climate Assessment,e251f590-177e-4ba6-8ed1-6f68b5e54c8a contributing to our understanding of the impacts of climate change on phenological events. Many studies, in many areas, have shown significant changes in phenology, including spring bud burst, emergence from overwintering, and migration shifts. A key uncertainty is “phase effects” where organisms are so out of phase with their natural phenology that outbreaks of pests occur, species emerge and cannot find food, or pollination is disrupted. This will vary with specific species and is therefore very difficult to predict.03297bb4-3833-4606-ae88-a166d29b7288 b0ab019c-3ea7-4e75-986c-2cc74541c187 37f4c175-f826-4106-8f9e-1661f51a470c

Assessment of confidence based on evidence: Given the evidence base and uncertainties, there is very high confidence that the timing of critical events, such as spring bud burst, emergence from overwintering, and the start of migrations, has shifted, leading to important impacts on species and habitats.

References :

• Changes in spring arrival of Nearctic-Neotropical migrants attributed to multiscalar climate (f5e7f46d)
• Changes in the Onset of Spring in the Western United States (a454cc19)
• Northern Hemisphere Modes of Variability and the Timing of Spring in Western North America (56447233)
• Variable shifts in spring and autumn migration phenology in North American songbirds associated with climate change (7fb94ff1)
• An examination of synchrony between insect emergence and flowering in Rocky Mountain meadows (241f3e50)
• Global Climate Change Impacts in the United States (e251f590)
• Bird migration times, climate change, and changing population sizes (eeb20593)
• Examining the onset of spring in Wisconsin (a7b4b70b)
• Fingerprints of global warming on wild animals and plants (37f4c175)
• A globally coherent fingerprint of climate change impacts across natural systems (b0ab019c)
• Flowering phenology change and climate warming in southwestern Ohio (bab55be2)
• Climate warming causes phenological shift in Pink Salmon, Oncorhynchus gorbuscha, behavior at Auke Creek, Alaska (699a7dbf)
• Onset of spring starting earlier across the Northern Hemisphere (655d6652)
• Influences of species, latitudes and methodologies on estimates of phenological response to global warming (03297bb4)
• Climate and the complexity of migratory phenology: sexes, migratory distance, and arrival distributions (d5af6e55)
• The phenology mismatch hypothesis: are declines of migrant birds linked to uneven global climate change? (f8043f85)
• Phenology as a Bio-Indicator of Climate Change Impacts on People and Ecosystems: Towards an Integrated National Assessment Approach. (13f67e66)
• Shifts in the flowering phenology of the northern Great Plains: Patterns over 100 years (5bb98e9a)
• Impacts of Climate Change on Biodiversity, Ecosystems, and Ecosystem Services. Technical Input to the 2013 National Climate Assessment (7406884d)