4) Threats to biodiversity
Study linking habitat destruction to biodiversity loss
(From Applied ecology) SODHI ET AL 2004 Southeast Asia has the highest relative rate of deforestation of any major tropical region, and could lose three quarters of its original forests by 2100 and up to 42% of its biodiversity.
What is causing a rise in our need to produce food?
1) MORE PEOPLE TO FEED: UN (1999) estimates that global population will rise to 9 billion by 2050 (= more food demand) Global daily calorie intake has already risen 27% in the past 50 years (data from FAO). Trends particularly worrying in some countries - intake in China has doubled in this timeframe (FAO). 2) CHANGES IN DIET: TILMAN AND CLARK (2014) [not in notes] Rising incomes/urbanisation are driving a global dietary transition, with more consumption of refined sugars, refined oils, fats and meats. CONSUMPTION of these foods correlates with PER CAPITA INCOME. The dietary transition is a major contributor to increases in g.g. emissions, land clearing, as well as health problems such as type II diabetes and coronary heart disease. See applied ecology, William Foster lectures - 2) is actually outweighing 1).
Further evidence of prehistoric human over-exploitation (from applied ecology)
1) OWEN-SMITH 1987 % genera to go extinct in the last 130,000 years increases with body mass range (kg). Could be due to factors such as slow reproductive rates, but also due to larger genera being preferentially selected by hunters. Evidence for this view: SANDOM ET AL 2014 (see conservation lecture 1) 2) MARTIN 1984 Large decreases in percentage survival of large animals (mammals, reptiles, birds in the last 100,000 years appear to coincide with the arrival of efficient human hunters.
What is the living planets index?
An attempt at measuring changes in global biodiversity. Designed to test whether we are 'reversing the rate of biodiversity loss' under the Convention for Biological Diversity Pros: based on multiple data sets looking at changes in abundance, not just number of species (therefore a better measure of biodiversity than simply considering species richness). Cons: Uses vertebrates only (best data sets and less variable). Loh et al (2005) state that birds and mammals are over-represented, relative to other vertebrate classes (extra reading, not in notes)
Most severe type of pollution effects
Climate change - see lecture 5
General evidence for humans being associated with over-exploitation
DARIMONT ET AL 2015 Suggest that humans are an ecologically unsustainable 'super predator' due to high levels of over-exploitation Used over 2000 estimates of exploitation rate, found that humans kill adult prey at median rates that are up to 14 times higher than other predators. Highest exploitation rate is of terrestrial carnivores and fishes. Evidence for human over-exploitation having effects, even prehistorically, see below
Example of pollution affecting habitats
Deepwater Horizon oil spill, 2010: 4.9 million barrels of crude oil (according to the on scene coordinator report) = largest accidental marine oil spill of all time ~7,000 dead animals collected overall (short term impact) Long term impact more complex (see below) Other examples - see applied freshwater ecology
Information on habitat fragmentation, and evidence for the effects it can have
Evidence for fragmentation: HADDAD ET AL 2015 Satellite analysis of global forest cover: 70% of remaining forest is <1km from the edge, therefore 'subject to degrading effects of fragmentation' Effects of fragmentation: 1) HADDAD ET AL 2015: Synthesis of experiments from the past 35 years suggests that fragmentation reduces biodiversity by 13-75%, and impairs ecosystem functions by decreasing biomass/nutrient cycles. 2) more general effects of degredation, see MEA 2005 (below)
Specific example of over-exploitation (second horseman)
Fish stocks - EUROPEAN ENVIRONMENT AGENCY (2014): 58% of assessed commercial fish stocks are NOT in 'good environmental status', implying that some degree of over-exploitation is occurring. "The use of commercial fish/shellfish stocks in Europe, therefore, remains largely unsustainable" Also - 30% of marine fish stocks are overfished, up from 10% in 1974 (FAO, 2014)
Evidence for light pollution
GASTON ET AL 2013 Nightime lighting could potentially affect "all levels of biological organisation, from cell to ecosystem" Specific examples: owl spp - affects location of prey syrian hamster - affects circadian rhythm Leaf-eared mouse - reduced nocturnal activity Pond bats - reduced feeding rates American robin - earlier initiation of singing Atlantic salmon - altered timing of nocturnal migration.
Current trends in ecological footprints
Globally, humanity's per person Ecological Footprint decreased 3 percent during 2008 and 2009 global financial crisis, due mostly to a decline in demand for fossil fuel and hence a decreasing carbon Footprint. (Decreased in high income countries but stayed stable in middle/low). High income countries, on average, have higher ecological footprints than middle income countries, which have higher ecological footprints than low income countries. Examples - takes 2.5 Chinas to support China, - worst = takes 7.1 Japans to support Japan. All info from Global footprint network, 2014
What information does the living planet index tell us?
LIVING PLANET REPORT, 2014 LPI suggests a biodiversity decline of 52% from 1970 to 2010 Declines seen in freshwater, marine and terrestrial spp. but most severe are in freshwater spp. Large differences between temperate areas (where overall increasing) and tropical areas (where considerable declines).
Evidence for the long term impact of Deepwater Horizon Oil spill
Long term impacts not always that bad: MCCALL/PENNINGS 2012 Intertidal crabs and terrestrial arthropods were suppressed in 2010 even in seemingly unaffected areas, but littoria snails unaffected BUT - one year later, crabs/arthropods had largely recovered to pre-oil spill levels. Suggests that some habitats/spp. can recover quickly - "arthropods are both quite vulnerable to oil exposure and quite resilient"
Evidence for nitrogen pollution effects
MASKELL ET AL 2010 Study of British habitats - significant reduction in species richness with N deposition in a variety of studied habitats - reasons why this occurs varies according to habitat: Acid grassland/heathland - evidence from trait changes suggested that acidification rather than increased fertility was responsible for species loss. calcareous grassland - evidence of eutrophication in response to increasing N deposition.
Evidence for habitat degradation (as opposed to habitat destruction) being linked to extinctions (from applied ecology)
MILLENIUM ECOSYSTEM ASSESSMENT 2005 With increasing levels of land use intensity (representing increasing habitat degradation), estimated population sizes of animal and plant groups tends to decrease (birds, amphibians, reptiles, mammals, plants). NB: not completely true = e.g. urban land use seems to have higher amphibian population sizes than plantation land use - reflects the fact that human environments can create new habitat for some taxa.
What is an ecological footprint?
Measures the total amount of BIOLOGICALLY PRODUCTIVE land/sea AREA an individual/region/all of humanity/a human activity requires to PRODUCE THE RESOURCES it consumes and ABSORB the CO2 emissions, and COMPARES this to the amount of land/sea area that is available. (according to the Global footprint network)
Evidence for rising food demand
Overall - FAO 2012 Global calorie intake has increased by 27% in the last 50 years - doubled in China in this time frame. Greater demand for meat - FAO 2012 Meat production has increased ~4 times in the last 50 years, with ~30 fold overall increase in Asia alone. Increase in meat production per capita is 15 fold in Asia - shows the effects of changing diets. (Wild fish consumption declining but farmed fish more than compensating.) (Mutton and beef consumption stable but very large increases in chicken and pork consumption.)
Examples of invasive species (third horseman)
PATHOGENS e.g. ash dieback (Chalara) - first discovered in England from infected trees originating from a nursery in the Netherlands. FORESTRY COMMISSION, 2015: 23% of 10k squares sampled in the UK have confirmed Chalara infections in the wider environment. MARINE INVASIVE - GREEN ET AL 2012 - Invasive Indo-Pacific lionfish in the Atlantic - increase in lionfish abundance coincided with a 65% decline in the biomass of the lionfish's 42 Atlantic prey fishes in just two years TERRESTRIAL INVASIVE - Euglandina rosea snails introduced in Pacific Islands to control African Land Snail, but also prey on native Partula snails. Since then, 51 Partula Species have become extinct, 11 have become extinct in the wild and 13 are critically endangered (IUCN). MURRAY ET AL 1998 state that all species of Partula on the island of Moorea have been made extinct as a result of Euglandina introduction.
What is the evil quartet?
Phrase coined by Diamond (1984). AKA the four horseman of the ecological apocalypse - describes four ways in which human activity causes loss of biodiversity: 1) Habitat destruction, including pollution 2) Over-exploitation 3) Invasive Species 4) Extinction Cascade (NB in reality they are all linked).
Why is the actual impact of pollution difficult to quantify?
There are often complex effects that could potentially go unnoticed. E.g. Deepwater Horizon oil spill - BRETTE ET AL 2014 crude oil samples from the spill experimentally found to prolong cardiomyocyte action potentials in tuna, by blocking the delayed rectifier current (= creating cardiotoxicity/arrhythmias). Other examples - complex effects of toxins in UK freshwaters (see applied ecology).
Evidence for extinction cascades (final horseman)
This is more a potential consequence of effects from the other three horseman. Extinction cascades can often occur where there are strongly interacting networks in ecosystems. Example - ESTES ET AL 1989 (not in notes) local extinctions of sea otters in North Pacific ocean thought to have lead to deforestation of kelp beds due to increased grazing by herbivorous sea urchins, one of the otter's main prey. Caused various cascading effects resulting from the biological and physical importance of kelp in coastal ecosystems. These interactions probably were important agents of selection for certain species (so linked to secondary extinctions). Local extinctions included that of urchins themselves - formation of "urchin barrens" where no life is present. Another example - MELLO ET AL 2011, in notes Investigated mutualistic relationships between fruit bats and fruit plants (bats eat fruit and pollinates) Relationships largely follow genus-genus associations (a single genus of bat pollinates a single genus of plant) with a few exceptions. Suggests that extinctions of bat species could cause 'larger changes in network structure' i.e. extinction cascades possible
Information on habitat destruction
Tropical forests - ACHARD ET AL 2002: Satellite data suggests ~5.8 million hectares of tropical forest were deforested each year between 1990-1997, with a further ~2.3 million hectares visibly degraded Rates also appear to be increasing - DeFries et al 2002 satellite data suggests a 10% increase from 1980s to 1990s, most notably in SE Asia. Hansen et al 2013 suggest that deforestation is increasing now in the tropics, based on landsat data. Also applies to less well known habitats: (1) REPUBLICA ORIENTAL DEL URUGUAY, 1992 loss of S. American grasslands - 80% of grasslands in Uruguay are now used for cattle ranching 2) Cerrado (Brazil) affected by cattle ranching/soy production - minimal protection and fast being lost, second only to Atlantic forest for vegetation loss. 3) RIBEIRO ET AL 2009 Brazilian Atlantic Forest - only 1% of the original forest is protected, and 88% has been lost.
