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Unformatted text preview: ANT 154BN Course notes Lecture #19: Concluding remarks: Conservation 10 March 2011
Key terms and concepts are indicated in blue Outline: Three simple questions
1. Should we focus solely on pristine forests? 2. Are all forest species affected equally 3. Are all forests created equal? 1. Should we focus solely on pristine forests?
results from a recent study of orangutans • orangutans have lost 80% of their habitat in the last 20 years • The remaining patches of undisturbed lowland forest on Borneo are shrinking and becoming increasingly fragmented. Orangutan populations in these fragments are small and therefore vulnerable to extinction N0 = 50 N0 = 100 N0 = 250 N0 = 500 Marshall et al. 2009 ANT 154B Lecture #19 course notes Can orangutans survive and reproduce in logged forests? East Kalimantan as a test case page 2 of 5 Results are equivocal. Methods 2001-2004, n=762 transects (381 km) at 22 sites Recorded nest density, habitat disturbance, assessed habitat quality Village surveys to determine hunting pressure Results: hunting is the real threat Results: hunting is the real threat Conclusion: orangutans are extremely susceptible to population declines due to hunting, but tolerant of moderate levels of logging. (a) O R A N G U T A N P O P U L A T I O N B I O L O G Y, L I F E H I S T O R Y, A N D C O N S 200
Population size 100 Population simulations
Hunting pressure (% population lost/yr) populations are expected to experi and reduction in K (Arut Belantik and Samba-Kahayan, 20% decli populations, Mawas and Sebanga lose habitat until the orangutan extirpated. An increase in availab sible at Tanjung Puting, which wo to lead to increase in population si Population size 100 100 Population size 200 200 0% 1% 3%
200 400 600 800 1000 22.2.3. 5 West K alimantan and Saraw Six of the habitat units in West K Sarawak are estimated to be suf c capable of continuing to support d and genetically healthy populat habitat unit at Bukit Baka (N also appears able to persist, althou ished genetic diversit y. Marshall et al. 200 2 2 . 2 . 3 . 6 S ab a h The survey work of Ancrenaz N0= 250; lines mean of provides evidence that some popu Marshall et al. 2009 500 simulations Marshall et al. 2009 aged forests (e.g., Tabin, Trus M Conservation implications 100 Foundation) are likely currently be 1. Light to moderate logging is compatible with orangutan conservation. et al. 2004b, 2005). In contrast, th 2. Proximity to humans per se does not have negative effects. Kulamba is estimated to be at a s than double the carrying capaci 3. Conservation efforts should focus on eliminating hunting. 800 0 200 400 600 1000 tat. Similarly, the populations in Years 4. The conservation value of lightly degraded forests must be publicized, so they are protected from forests of Lower Kinabatangan ar additional logging, burning, or clear-cutting. Figure 22 . 3 Impac ts of hunting on population size. Traces show above K, and to currently have an 5. Addition of degraded ef fec t s oto iexisting nting rates on VORTE X modesubstantially increase the amount of the forest f d f ferent hu protected areas would ls of Bornean due to the sex bias in dispersal bet suitable habitat available for orangutans. orangutan populations in high-qualit y (a), medium-qualit y (b), We examined the impact of comp and low-qualit y habitats (c). In each plot lines show, from top to isolation of fragments. When com bot tom, the ef fec ts of hunting that removes 0%, 1%, 2%, and 3% the smallest fragments do not c of the population annually. Lines plot mean population size of 500
Time (years) (c) ANT 154B Lecture #19 course notes Methods page 3 of 5 2. Are all forest species affected equally Sensitivity to logging of 41 Bornean mammal species classiﬁed as:
• Tolerant: Positive effect of logging, i.e., densities increased by more than 20 percent within the ﬁrst year after logging. • Neutral: No recorded effects from selective logging, i.e., no signiﬁcant changes (<± 20%) in densities following logging. • Intolerant: Severely impacted by selective logging, i.e., densities decline by more than 20 percent in the ﬁrst year after logging, and do not recover within 5 years after logging.
Species differ in their responses to habitat degradation. + 20%
change in population density 0% - 20% Prelogging Postlogging tolerant neutral intolerant Summary of general patterns
Tolerant species • use all vegetation strata • generalized diets younger Intolerant species • strict tree canopy dwellers • specialized diets older
Conservation implications 1. While most species are tolerant of well-managed, sustainable logging, those that are most negatively affected are those that are also most vulnerable to extinction. 2. Evolutionary history may allow us to predict which species are most likely to be adversely affected by logging. ANT 154B Lecture #19 course notes page 4 of 5
10 9 8 7 6 5 4 3 2 1 0 A Gibbon sources and sinks Source-sink population dynamics Habitats vary & reproductive output (“r”) depends on habitat quality at Gunung Palung? Group density score (individuals/km2) 3. Are all forests FIGURE 3.equal? created B r > 0 = Source r < 0 = Sink Density by forest type
(# individuals/km ) In a habitat mosaics, sink populations can persist because of immigration from 400 600sources nearby 0 200 800 1000 2 2
(# individuals/km in territory) (# individuals/group) Altitude midpoint of territory (m
asl) Territory quality Group size Group density score (individuals/km2) E 3. n = 7 forest types, R2 = 0.72, p = 0.02 10 9 8 7 n = 33 groups, R2 = 0.81, p < 0.0001 n = 33 groups, R2 = 0.50, p < 0.0001
6 A B C 5
Group size 6 5 4 3 2 1 0 0 200 400 600 800 1000 Altitude midpoint of territory (m asl) 4 3 2 0 200 400 600 Altitude (m asl) 800 1000 Group density score (individuals/km2) 10 9 8 7 6 5 4 3 2 1 0
Time with no offspring IBI Birth offspring #2 Birth offspring #1 Birth 37 B
Death RLS = TLS – AFR Marshall 2009 Biotropica 5
F1#1 AD 4
Dispersal offspring #1 3 F1#2 Dispersal offspring #2 2
PN=2(F=0) = RLS – (IBI + AD) 0 200 400 600 800 1000 Altitude midpoint of territory (m asl)
Time with one offspring F1#1 0 200 400 600 Altitude (m asl) 800 1000 RLS 37
F1#2 PN=2(F=1) = 2 * IBI RLS 6 C 5 Time with two offspring F1#1 & F1#2 PN=2(F=2) = AD – IBI RLS Group size 4 Some “source habitat” biases High reproductive rate High population density 3 2 0 High food availability
200 400 600 Altitude (m asl) 800 1000 37 ANT 154B Lecture #19 course notes Conservation implications page 5 of 5 1. It is important to preserve the full complement of habitats that a species occupies. 2. Rapid surveys may be misleading. 3. Beware results from studies conducted in high quality habitats. Take home messages
1. Degraded forests can retain high conservation value. 2. Some, but not all, vertebrate species can persist in degraded habitats. 3. Species occupy habitats that cannot support them in the long term. Questions to ponder
1. Should we focus solely on pristine forests? 2. Are all forest species affected equally 3. Are all forests created equal? ...
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