6. Global change in island ecosystems Flashcards
Structure of lecture
What are the 3 types of island?
1
- Volcanic (e.g., Madeira, Galapagos)
- Land-bridge (e.g., Britain, Tasmania)
- Continental fragment (e.g., New Zealand, Madagascar)
What are the 6 factors defining the importance of islands?
2
- Land-mass
- Hotspots for scientific research
- Global economics
- Species richness
- Museums/cradles of biodiversity
- High species richness
How much of the global surface do islands cover?
2.1
6.7% of Earth’s surface
10% of world’s population
25% of nations
How are islands important for scientific breakthroughs?
2.2
Immense species richness, geological diversity, linguistic diversity, unique geography.
e.g., Darwin’s trip to the Galapagos
How are islands important for global economics?
2.3
Islands, as well as being rich and powerful themselves, can influence the delineation of exclusive economic zones across the world, and thus stake territorial claims over the planet’s ocean.
i.e., islands add an extra 1.1Mkm2 to the 0.3Mkm2 land mass of Portugal
How are islands important for species richness?
2.4
20% of the world’s biodiversity comes from islands. Intense adaptive/non-adaptive radiations. Landscape for speciation
How are islands important for linguistic diversity?
2.5
27% of all human languages are spoken on islands. Language diversity relates strongly to island area and isolation
How do islands act as harbours of ancient biodiversity?
3
- Evolutionary cradles
- Hotspots for endemic taxa
- Adaptive radiations
- Unique community assembly
- Unique morphologies
How do islands act as evolutionary cradles?
3.1
Offers the opportunity for phenomena such as intra-archipelago speciation, genetic separation from mainland, heterogeneity and natural fragmentation of populations
How are islands important for adaptive radiations?
3.2
Archipelagos provide the perfect opportunity for the rapid diversification of a single lineage into many species that inhibit a range of environments, use a variety of resources and differ greatly in traits.
Isolation, number of islands, location, resources etc., all important
How are islands unique in terms of community assembly?
3.3
Special dispersal and establishment on different islands. This leads to regional processes that drive different community assembly, such as abiotic and biotic factors, extinction, diversification and speciation.
What leads to the fragility of island ecosystems?
4
- Natural disasters
- Small distribution ranges
- Natural population fragmentation
- Low population sizes (N)
- Few populations
- Limited genetic diversity
- Island syndrome
How are islands impacted by natural disasters?
4.1
Highly likely to face meteorological and geological disasters, such as volcanic eruptions, landscapes, hurricanes and wildfires due to unstable geographic position.
Each disaster can damage a large proportion of an island, and its endemic species.
However, natural disasters can also create opportunities and lead to diversity in the long term
How are islands at risk from small distribution ranges?
4.2
This can lead to a high extinction risk from stochasticity and natural disasters, and lower population sizes (unless density compensated)
How are islands at risk from low population sizes?
4.3
Low effective population sizes (individuals contributing to the population), and high risk of stochastic demographic collapse
How are islands at risk from having few populations of each species?
4.4
High intra-specific competition due to the nature of small islands. Leads to inbreeding depression and population collapse.
How are island populations at risk from limited genetic diversity?
4.5
Populations form from the founder effect, and are at risk from genetic bottleneck. Species are at risk from low and singular genetic diversity
How are island populations at risk from the island syndrome?
4.6
Community level: Low species richness, disharmonic biota, high endemicity, few interactions
Species level: Dwarfism, gigantism, slow lifestyle few predators/prey, flightlessness, stoutness, tameness, loss of hunting ability, loss of defenses
What are the human impacts on island ecosystems?
5
- Habitat loss and fragmentation
- Overexploitation
- Invasive alien species
- Climate change
- Wildfires
These factors are highly synergistic
How are humans contributing to habitat loss and fragmentation on islands?
5.1
Deforestation is changing ecosystem connectivity. Watson et al., 2004 showed that human activity in Madagascar has led to >90% forest loss, and extinction of >25% of endemic bird species. Leading to increasingly small and far between habitat fragments with low connectivity. Contributing to fewer populations and lower genetic diversity
Nogue et al., 2021 looked at the pollen fossil record and showed that humans have accelerated floral compositional turnover
How has human overexploitation harmed island species?
5.2
I.e., direct hunting/poaching etc.,
Hansford et al., 2018 showed that human arrival to Madagascar 10,500 years ago may have contributed to extinction of elephant birds via hunting
How are invasive species harming island species?
5.3
Leading to either direct impacts (i.e., predation) or indirect changes (i.e., disease and ecological changes)
The introduction of the brown tree snake in Guam has resulted in the extinction of >10 native bird species
How is climate change harming island species?
5.4
Species cannot take the usual escape options of migration and rangee shifts. This means that species are more likely to disappear as a result of climate change.
Patino et al., used stratified random sampling on Madeira and found that forest fires caused by climate change are having a large impact on landscape composition
How are wildfires harming endemic island species?
5.5
Destruction of endemic species, their habitats, their prey etc., Ecological disruption
Destruction of sampling sites for science.
Give an example of how human impacts on island can be synergistic
5.6
Benning et al., 2002 showed that the abundance of native birds in Hawaii is under the influence of mosquito parasites and their vector. Climate change is accelerating the spread of these parasites into higher latitudes and elevations, and the birds have nowhere to go…
What are the major methods we can use to restore island habitats?
6.1
- Increasing knowledge
- Conservation of threatened species
- Habitat restoration
- Management of invasive species
- Surrogate species
How can increasing knowledge help in the conservation of island species?
6.1
Use of indigenous and traditional knowledge
Understanding and improving scientific knowledge
Improving public education and understanding
Use of technology for monitoring
i.e., 60% of al bat speices occur on islands, and 25% are endemic. Most of these species have >2 papers written abut them. The decline of many bat species, such as the Christmas Island Pipistrelle, could be attibuted to a lack of scientific understanding
How can the management of invasive species protect island species?
6.2
Eradication of invasive mammals on islands has the potential to result in immense population gains, and habitat restoration.
e.g., the removal of rats and goats from islands in Madeira allowed for the massive increase in the numbers of critically endangered ground lizards from 2012 to 2017
How can we use surrogate species to protect endangered island organisms?
6.3
Use of a species with a similar niche to fill the ecoogical niche and prevent ecosystem collapse
