Habitat Degradation & Loss

Data for Galapagos plants from van der Werff (1983) Vegetatio Species-Area Curves No. species A very consistent pattern of organismal distribution Area

Data for Galapagos plants from van der Werff (1983) Vegetatio Area Log 10 (Area) No. species Log 10 (No. species) y = 30.4 x 0.31 R² = 0.78 y log = (0.31 x log ) R² = 0.78 Log 10 (y) = Log 10 (30.4 x 0.31 ) y log = Log 10 (30.4) + (0.31 Log 10 (x)) Species-Area Curves

Map from Photo by Christian Ziegler from Barro Colorado Island Species-Area Curves

Data from the 50-ha Forest Dynamics Plot on Barro Colorado Island, Panama Area Log 10 (Area) No. species Log 10 (No. species) Species-Area Curves

Whittaker rank-abundance curve Data from the 50-ha Forest Dynamics Plot on Barro Colorado Island, Panama Rank Log 10 (No. individuals) Most species are rare! Relative-Abundance Distributions

See: Rabinowitz et al. (1986) in Soulé, ed., Conservation Biology XX X XX XX WideNarrow Habitat specificity BroadRestrictedBroadRestricted Local population size Somewhere large Everywhere small Seven Forms of Rarity Most species are rare, but rarity can be defined in various ways Geographic distribution

Rare species are especially vulnerable Small populations are especially prone to extinction from both deterministic and stochastic causes Image of extinct Hawai’i ’Ō’ō (Moho nobilis) from Wikipedia

E.g., Hawaii’s native bird species Half of the remaining species went extinct soon after Captain James Cook arrived (in 1778) Half went extinct soon after the Polynesians arrived (in ~ 300 A.D. / C.E.) Image of extinct Hawai’i ’Ō’ō (Moho nobilis) from Wikipedia Rare species are especially vulnerable Small populations are especially prone to extinction from both deterministic and stochastic causes

∆N ∆t = B - D Rare species are especially vulnerable In a closed population (i.e., no immigration or emigration) of size N, the change in population size for a change in time, where B = births, and D = deaths, is: Small populations are especially prone to extinction from both deterministic and stochastic causes Remember the “BIDE factors”: birth, immigration, death & emigration

∆N ∆t = b(N) – d(N) ∆N ∆t = (b-d)(N) Rare species are especially vulnerable Small populations are especially prone to extinction from both deterministic and stochastic causes In a closed population (i.e., no immigration or emigration) of size N, the change in population size for a change in time, where b = per capita birth rate, and d = per capita death rate, is:

∆N ∆t = r(N) If r>0, N grows; if r<0, N declines; if r=0, N does not change Rare species are especially vulnerable Small populations are especially prone to extinction from both deterministic and stochastic causes Substitute r for (b-d), where r = per capita growth rate:

Example, r = –0.5 : Population A Population B N A,t = 1000 N B,t = 10 N A,t+1 = 500N B,t+1 = 5 N t+1 = N t + ∆N ∆t Rare species are especially vulnerable Small populations are especially prone to extinction from both deterministic and stochastic causes

Deterministic  r < 0 Genetic stochasticity Demographic stochasticity  individual variability of r (e.g., variance) Environmental stochasticity  temporal fluctuations of r (e.g., change in mean) Catastrophes Rare species are especially vulnerable Small populations are especially prone to extinction from both deterministic and stochastic causes

Demographic & Environmental Stochasticity Demographic Stochasticity Each student is a sexually reproducing, hermaphroditic, out-crossing annual plant. In the first growing season (generation), each student mates (if there is at least 1 other individual in the population) and produces 2 offspring. Offspring have a 50% chance of surviving to the next season. Flip a coin for each offspring; “head” = lives, “tail” = dies. Note that average r = 0; each parent adds 2 births to the population and on average subtracts 2 deaths [self & 1 offspring – since 50% of offspring live and 50% die] prior to the next generation. In a large pop. (e.g., whole class), heads and tails average out to give r=0 (no change in pop. size). When class is sub-divided into small sub-populations (e.g., 2 individuals each with no migration), some will have less than 2 live individuals after the coins are flipped to determine survivorship to the next growing season (the next generation).

Habitat Destruction, Loss, Degradation… At least 83% of the Earth’s land surface has been transformed by human activities (Sanderson et al. 2002) About 60% of Earth’s ecosystems are considered degraded or unsustainably used (Millennium Ecosystem Assessment 2005) 98% of U.S. streams and rivers have been fragmented (see next lecture) by dams (Benke 1990)

Habitat Destruction, Loss, Degradation… Habitat degradation – impacts that affect many, but not all species; some of which may be temporary Habitat destruction & loss – impacts that affect nearly all species; time scale for recovery is very long How do humans destroy & degrade habitats & ecosystems? E.g., agricultural activities, extraction activities, certain kinds of development These are often considered to be the most important direct threats to biodiversity, since they eliminate species, reduce population sizes, and reduce performance of individuals

Image of shrinking forest cover on Borneo from Habitat Destruction, Loss, Degradation… Loss of forest habitat in Borneo

Image of Louisiana land loss (historical & projected; ) from Habitat Destruction, Loss, Degradation… Loss of terrestrial coastal habitats in Louisiana

Map from Habitat Destruction, Loss, Degradation… Degradation of marine and coastal habitats in Louisiana Deepwater Horizon – drilling rig explosion on April 20, 2010

Halpern et al. (2008) Science; see Habitat Destruction, Loss, Degradation… Anthropogenic degradation of oceans

Images from Minimum sea ice concentration; 9% decline per decade Habitat Destruction, Loss, Degradation… Loss of ice from polar ice cap

Pollution is a Form of Habitat Degradation Light pollution Air pollution & acid rain Solid waste & plastics Chemical pollution (e.g., DDT, endocrine disruptors)

Photo from Wikipedia Pollution is a Form of Habitat Degradation Rachel Carson (1907 – 1964) Silent Spring (1962) – motivated creation of the U.S. Environmental Protection Agency

Image from Pollution is a Form of Habitat Degradation Theo Colborn (b. 1927) Theo Colborn, Dianne Dumanoski & John P. Meyers (1997) Our Stolen Future: How We Are Threatening Our Fertility, Intelligence and Survival

Pollution is a Form of Habitat Degradation Light pollution Air pollution & acid rain Solid waste & plastics Chemical pollution (e.g., DDT, endocrine disruptors) Excessive nitrogen inputs Eutrophication Etc…

Image from Pollution is a Form of Habitat Degradation Excessive nitrogen inputs & eutrophication

Image from Pollution is a Form of Habitat Degradation Excessive nitrogen inputs & eutrophication contribute to coastal hypoxia (i.e., the “dead zone” phenomenon) every summer off Louisiana’s coast

Figure from Myers et al. (2000, Nature) Biodiversity Hotspots Usually defined by species richness, endemism & threats These hotspots of biodiversity cover only ~1.5% of the Earth’s land; if they were destroyed ~1/3 of Earth’s species would go extinct

Map from Biodiversity Hotspots Usually defined by species richness, endemism & threats

Image of oiled pelicans on June 3, 2010 from the Gulf of Mexico from Wikipedia Biodiversity Crisis Whether or not habitat degradation or loss occurs in a biodiversity hotspot, any resulting biodiversity losses contribute to the global phenomenon, since local losses aggregate to produce the global crisis.