Download Climate Change and Migration

Climate Change and Migration
Hayes et al. 2004
Erin McMichael
Spring 2009
What is Migration?
• The seasonal movement between two geographic locations that is related to the reproductive cycle, changes in temperature, and prey availability (Forcada 2002) • The persistent movement between two destinations (Cockeron and Connor 1999)
• The mass directional movements of large number of a species from one location to another (Thain and Hickman 2000) • Characteristics of Migration (Dingle 1996)
–
–
–
–
–
Persistent movements between distant sites
Directional movement
Inert behavior to arresting stimuli
distinct behavior for departure and arrival
Energy allocation (ie migratory fueling)
Convention on Migratory Species (CMS)
• Migratory Species ‐ a significant proportion of whose members cyclically and predictably cross one or more national jurisdictional boundaries
• Example: baleen whales (blue, grey, fin, right, humpback) – undertake long seasonal migrations between tropical calving grounds in winter and high latitude feeding grounds in summer
– annual grey whale migration 15,000‐20,000 km summer feeding grounds in Arctic winter breeding grounds in the south (Jones and Swartz 2002)
Basics of Migration
• Evolutionary adaptation to changing environmental conditions
– the basic driving forces are ecological and biogeographic factors • (seasonality, spatiotemporal distributions of resources, habitats, predation and competition)
• Triggers/ Cues
–
–
–
–
may relate to changes in day length timing of migrations can vary from year to year
prey abundance may also be an important factor
temperature and sea ice formation can also be influential (Stern 2002)
• Phenotypic Plasticity (Alerstam 1990; Berthold 2001)
– individuals are likely to differ to some degree in the extent to which they migrate – proportion of the population that does migrate may vary through time
– amongst species there is an almost continuous spectrum from those that are entirely sedentary to those composed entirely of long‐distance migrants (Siriwardena et al. 2002)
Types of Migration
• leap migrants
migrate in long‐haul journeys stopping at only a few, usually discrete sites often in large numbers (avian species)
• broad‐front migrants
Hopkins Marine Station
migrate in short hops, stopping frequently on route, and often have geographically diffuse migration routes (bats, insects, passerine birds and marine animals)
(UNEP 2006)
Migrating Species are Particularly at Risk
• travel large distances
• subject to a wide range of environmental influences
• rely on a wide range of natural resources
• likely to be affected by climate change at some point of their life cycles
• global climate change will affect the physical, biological and biogeochemical characteristics of the oceans and coasts
(Robinson et al. 2005)
Changes in Climate That May Affect Migration
• Increase in temperature
• Ocean circulation – predict a weakening of the Gulf Stream during the 21st century
• 25% by 2100
•
•
•
•
•
•
•
•
•
Sea level rise Changes in salinity
Changes in climate patterns
Increase in CO2 concentrations
Ocean acidification
Decrease in sea‐ice cover
Increase in storm activity
Increase in wind speeds
Changes in wave conditions
FRS 1998; Hansen et al. 2001; IPCC 2001a; Sear et al. 2001; Hulme et al. 2002; FRS 2003; ICES 2004)
Effects on Breeding
• Longer reproductive periods (Crick et al. 1997)
• Longer productive periods in habitats • Earlier onset of reproductive maturity (porpoises, Read & Gaskin 1990)
• If a species has to take longer than normal on migration, due to changes in conditions en route, then it may arrive late, obtain poorer quality breeding resources (such as territory) and be less productive
• If migration consumes more resources than normal, then individuals may have fewer resources to put into breeding – large baleen whales may suffer from this, as they do not feed while on migration
• Alter breeding behaviors – Decrease in frequency and intensity of blue whales calls (Burtenshaw et al. 2004)
Change in Body Size
– Increase? • Due to increase in food availability (porpoises getting larger, Read & Gaskin 1990)
• Due to increase in growing season (Yom‐Tov & Yom‐Tov 2004)
How to compensate for extra mass during long migration? – Decrease?
• increasing habitat destruction and fragmentation leads to decrease in body size (Bergmann’s Rule)
• Limit ability to match change in climate (Thomas et al. 2004)
Decrease in survival ? Analysis of mammals during Pleistocene shows that body size decreases as temperatures increase. Mammals had larger body size with cold temperatures (Smith et al. 1995)
(Millien et al. 2006)
Phenology Mismatch • Changes in predator/prey may occur in terms of their distributions or in timing
– differential changes in developmental rates and can lead to a mismatch in timing between predators and prey
– Tuna in the Pacific (Polovina 1996) • Cascading Affects
– Earlier breeding (Crick et al 1997) (Crick & Sparks 1999)
• Alter cues (Millien et al. 2006)
Changes in Circulation/Upwelling
• Phytoplankton abundance/distribution (Hayes et al. 2005)
• Increase interaction between commercial fisheries and migrating animals
• Alter predator/prey abundance
• Alter species distributions
• Alter productivity
• Alter migration routes
– Wind
Migration Corridors • Migratory species need a coherent network of sites to facilitate their migratory journeys
• Changes in habitat quality (leading ultimately to habitat loss) is especially important on staging or stop‐over sites, as individuals need to consume large amounts of resource rapidly to continue their onward journey.
– high quality sites may crucial to allow migrants to cross large ecological barriers
– altering migratory fueling and ultimately survival
Evolutionary Potential
• Phenotypic plasticity
– Spectrum of number of individuals within a population that migrate
– Threshold exists that determine when one migrates that can be changed by selection
• Incidence and amount of migratory behavior is phylogenetically inherited (insects and birds) – Migratory behavior influences frequency of migratory behavior in young)
• Migration is, in part, genetic and as such there is genetic variation
– All individuals have genetic variation for all migratory populations regardless of phenotypic plasticity
• Species have the capacity to evolve as environments change
– Migration is an adaptation to varying climates
(Pulido et al. 1996)
Adaptability of Migratory Species?
• Genetic variance for the incidence of migratory activity that can change rapidly – (artificial selection, Berthold 1988) • Evolution favors birds breeding closer to wintering sites
– Selection favors non‐migratory individuals (evolution towards residency)
– Changes in migratory behavior are ‘easier’ for species that are at least partial residents
• species that migrate short distances can adapt faster and better
(Pulido et al. 1996)
Management and Conservation Laws
• The primary instrument for migratory species conservation is the Convention on the Conservation of Migratory Species of Wild Animals (CMS)
• Marine Protected Areas
– Current preserves may not be sufficient
– inflexible
The End