Impacts of global change on terrestrial and aquatic ecosystems

Rising sea levels

- 12% decrease in arctic sea ice per decade - IPCC products a 1m increase in sea level under low emission scenarios, however, even as high as 2m under low likelihood high impact scenarios along with ice sheet instability etc. - Just a 1m increase puts many coastal cities under threat

What is tropicalization

- CC causing many coral reef species to expand northward, following poleward flowing warmer currents - This causes the tropicalization of temperate regions that are being invaded by coral reef species which over-graze microalgae and impact the structure of the reef

Habitat loss

- Causes altered species abundances and extinction due to species-area relationships and small populations, which are prone to extinction due to environmental stochasticity, demographic stochasticity, genetic and allele effects

What do mesocosm experiments suggest about the effects of rapid warming?

- Dania Albini has been using machine learning to identify the effects of warming on thousands of plankton in ponds (ranging from 1-8 degrees above ambient) - Appears from data they decrease size with warming

Direct and indirect pathways that can transmit the impact of global environmental change among interacting species

- Direct and indirect effects ripple through food webs such that even species that aren't directly affected may still be affected by indirect pathways 1. Keystone predation - competitors share a keystone predators such that changes in predation on a competitor have indirect effects on the other prey 2. Apparent competition- Indirect competition due to sharing the same predator, if one prey does well so does the predator which increases competition on the other prey 3. Trophic cascade- effects cascade down to producer from keystone predator via herbivore

Why are ecosystem functions affected by changes in biodiversity?

- Drivers affect the composition and diversity of species - Species differ in their functional traits and so ecosystem functions are affected - altered functions also feedback to affect ecological communities

Why does species richness matter less than functional diversity?

- Evidence suggests that functional identity and diversity predict ecosystem functioning better than species-based indices - Land use intensification has been shown to have negative effects on FD in mammals, birds and plants

Habitat fragmentation

- Has negative effects beyond just habitat loss - causes reduced mobility between patches and extinction due to edge effects and population dynamics consequences of lack of connectivity/ subdivision which makes it difficult for individuals to move between component patches

Ocean acidification

- IPCC predicts a pH of 7.9-7.7 under medium-high emission scenarios - Oceans absorb CO2, creating carbonic acid in the water which binds with carbonate to make bicarbonate ions - Can cause existing carbonate to be dissolved, either way way less carbonate ions available in the ocean which affects organisms that rely on carbonates for their shells e.g. coral, echinoderms, sea urchins, calcifying algae and coccolithophores

Data regarding anthropogenic CC

- In 2021 the IPCC reported about a 1-1.5 degree increase above expected climate (under simulated natural conditions) from 1850 up to 2020 - Human activities are already having an effect on global surface temperature - Under a no change/ worst case scenario, CO2 emissions will double by 2050 and have risen by 4 degrees by then

How does body size change with temperature? (according to study)

- In aquatic larval stages of fly, body size declines with warming (James rule) - However, in other sites we see the reverse - Bergmans rule also supported in greenland

Drying lakes

- Lakes dry out due to CC - Since 1963, lake chad has shrunk to a 20th of its original size, has led to poverty in region that relies on fishing

Habitat degradation

- Maintains essential habitat structure but alters its suitability for different species, changing community structure and composition - almost always leads to habitat fragmentation

Extreme weather events

- Marien heatwaves - Heatwaves - Agricultural and ecological droughts

Example of emergent community-level consequences of climate change

- North Atlantic oscillations have an effect on wolf foraging behaviour - years where it is low, causing heavy snow and cold winters, wolves hunt in larger packs and number of moose killed per day increases - Moose abundance declines and growth of understory fir increases - Top-down trophic cascade modulated by natural climatic variations

Is the response consistent across regions?

- Others have found that organism size increases with warming in the same system- could this be because when there are sufficient resources to sustain larger consumers at higher trophic level warming does not favour the small?

Examples of diverse patterns in the arctic

- Patterns of shrinkage less common where organisms can keep up with rising metabolic demands - e.g seals increase because less ice means more hunting, diatoms increase, polar bears decline because ice needed for hunting

How do networks like food webs respond to species loss?

- Robustness of food webs to further perturbation increases with connectance - Rivet like threshold beyond which sensitivity is high - Food webs are more robust to the random removal of species than to selective removal of species with more links

how do changes in species interactions affect ecosystem-level dynamics

- Small tropical islands in Venezuela - Ecological meltdown caused by absence of top-down predation on small mammals e.g. rodents, vervet monkeys, iguanas etc.

How does diversity change with temp. based on this system?

- Species richness decreases with temp. across all sites - Some regional differences, seems there is a relationship between temperature and productivity as vertebrates in high productivity regions can keep up with rising metabolic demands

Change in stratification

- Stratification onset is decreasing- from 100 days to 80 days into the year

Evidence for interaction of climate change x biodiversity loss

- The combined effect of both pressures is predicted to lead to an average cumulative loss of 37.9% of vertebrate species - Synergistic effects indicated in overharvesting of timber and CC - effect more than sum of their parts and as a result measures targeting only primary effects are likely to be ineffective e.g. fragmentation can indirectly cause increased dryness and fire, releasing more GHGs and reducing habitat quality further

What are some ecosystem services?

- Timber for fuel, building, paper etc. - Non-timber forest products e.g. fruits, nuts, fibre, resin - Carbon sinks - Clean water - Flood prevention - Soil conservation - Ecotourism

Geothermal systems as natural experiments study

- Used geothermal systems as natural experiments - Streams with different temperatures (due to geothermal activity) in an area of about 1.5km - Studying them allows us to ask questions about CC and also relevant as this area is experiencing rapid warming

Warming of waters

- lakes warming 0.34 degrees per decade - trend may be driven by high altitude lakes (no ice cover)

Species-level consequences of global change

- move adapt or die - Adapt in situ via plasticity or evolution e.g. speckled wood butterfly - Shift distribution e.g. Polygonia C-album butterfly - Shift phenology

2 studies that provide evidence for earlier springs in seas

1. Arctic algal bloom peaks in June, used to peak in August/September 2. Metaanalysis of phenological change for different aquatic groups shows that all taxa are shifting their phenology about 4-5 days sooner a decade

2 key temperature size rules

1. Bergman's rule- within a taxonomic group larger animals will occur in colder environments e.g. bears 2. James's rule- within a species, larger individuals will be in colder areas e.g. antarctic lantern fish

2 studies that provide evidence for earlier springs in freshwaters

1. Endemic fish in tibet- otolith analysis shows they have more growing days than they used to and the reproductive phenology has advanced almost 3 days per decade 2. Mesocosm warming experiments show that warming causes larvae of western pondhawk to emerge up to a month sooner (5 degrees warming) and extend the emergence season

5 key drivers of biodiversity change (identified by the Millenium ecosystem assessment)

1. Habitat change 2. Climate change 3. Invasive species 4. Over-exploitation 5. Pollution (N and P) - climate change currently least threat but predicted to get worse - Habitat degradation/fragmentation is the biggest threat to biodiversity currently and has caused majority of past extinctions

3 universal responses to warming

1. Phenology 2. Range shifts 3. Size?

Examples that show positive relationship between biodiversity and ecosystem function

1. Responses of plant biomass to experimental manipulations of plant species richness at sites across Europe shows a clear positive correlation 2. Pollination services to coffee increase with richness of wild bees and proximity to natural rainforest habitat 3. In venezuela, smaller forest fragments have lower dung beetle species richness and lower dung burial rates + Lots of evidence for insurance hypothesis can be brought in- even if diversity not necessary it might be important in retaining service after perturbations/ in the face of change

what are the physical effects on climate change in marine ecosystems

1. Rising sea levels 2. Acidification 3. Extreme events

Physical effects of CC in freshwaters

1. Warming temperatures 2. Drying lakes 3. Rising levels 4. Changes in stratification

Response traits

Affect community structure and dynamics

Effect traits

Affect ecosystem structure and dynamics - refer to the functional contribution of component species to delivering an ecosystem function - issue is it is often correlated with response traits and so the most vulnerable species are also the most functional

What causes community-level consequences of global change

Emerge because different species respond differently to habitat change and the same groups often win a space which causes biotic homogenisation

Effect of such changes on ecosystem function (+example)

Habitat degradation alters food web interactions among species and alters their resilience to perturbation and the function they deliver - Example from Ecuador: the effect of increasing habitat modification along a land-use gradient on webs of bees and their pollinators was studied - the number of interactions dominating the food web decreases with increased habitat modification which is known to make habitats less resilient

What causes these size patterns- endo and ectotherms

In endotherms- smaller endotherms cope better due to larger surface area to volume ratio In ectotherms- warming increases metabolism which causes smaller adult body size and earlier maturation

Example of biotic homogenisation effects

Jari forest in brazil has 3 types of forest- primary, secondary and eucalyptus - Most species do best in primary but moths and fruit flies can survive in secondary and eucalyptus, causing biotic homogenisation in the eucalyptus forest as no other species can survive well there

Metabolic theory of ecology

MR varies with Mass^3/4 - Bigger animals need more energy to survive but they spend energy more efficiently so the relationship is not linear - In ectotherms, metabolic rate increases linearly with temp. - Animals can therefore reduce body size so that they need less resources to keep up with rising metabolic demands- for a given resource level (size would not change in response to warming if resources were infinite)

What might be some common solutions to different drivers of biodiversity loss (3)

The best way to mitigate the effects of CC might be to think in terms of habitat conservation and management 1. Improve habitat management - Increase pop sizes and reduce local extinction - New sites for colonists 2. Promote landscape level habitat heterogeneity - Enhances chances of species to stay within climate envelope through small-scale movements 3. Enhance habitat connectivity - Allow species to migrate to stay within their climate envelopes

Evidence for interaction between habitat change x CC effects

The threshold of CC below which species extinction occurs or populations decline is likely determined by the pattern of habitat loss - Biodiversity can shift distribution to track climate niches but fragmentation prevents this - the world is more fragmented for specialists (especially those with low dispersal ability) Example: butterflies in the UK, specialists have been unable to expand north as climate warms and discrepancy between area that is thermally suitable and currently colonised by butterflies is much larger