Passive restoration following ungulate removal in a highly disturbed tropical wet forest devoid of native seed dispersers

Nafus, Melia G.; Savidge, Julie A.; Adams, Amy A. Yackel; Christy, Michelle T.; Reed, Robert N.

doi:10.1111/rec.12559

Cited by 9 publications

(6 citation statements)

References 27 publications

(36 reference statements)

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“…Had Christy et al [ 10 ] searched less intensively on a given night in the snake enclosure on Guam, fewer snakes would have been found and the individual-based detection probability estimate(s) would have been lower. Because we obtained almost identical estimates nearly 1.5 years later in this area when corrected for effort but after substantial forest regeneration [ 17 ] and higher snake densities, we feel that the detection estimate per visual search effort unit ( = 0.07) is robust.…”

Section: Methodsmentioning

confidence: 90%

Inferring the absence of an incipient population during a rapid response for an invasive species

et al. 2018

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Successful eradication of invasives is facilitated by early detection and prompt onset of control. However, realizing or verifying that a colonization has occurred is difficult for cryptic species especially at low population densities. Responding to the capture or unconfirmed sighting of a cryptic invasive species, and the associated effort to determine if it indicates an incipient (small, localized) population or merely a lone colonizer, is costly and cannot continue indefinitely. However, insufficient detection effort risks erroneously concluding the species is not present, allowing the population to increase in size and expand its range. Evidence for an incipient population requires detection of ≥1 individual; its absence, on the other hand, must be inferred probabilistically. We use an actual rapid response incident and species-specific detection estimates tied to a known density to calculate the amount of effort (with non-sequential detections) necessary to assert, with a pre-defined confidence, that invasive brown treesnakes are absent from the search area under a wide range of hypothetical population densities. We illustrate that the amount of effort necessary to declare that a species is absent is substantial and increases with decreased individual detection probability, decreased density, and increased level of desired confidence about its absence. Such survey investment would be justified where the cost savings due to early detection are large. Our Poisson-based model application will allow managers to make informed decisions about how long to continue detection efforts, should no additional detections occur, and suggests that effort to do so is significantly higher than previously thought. While our model application informs how long to search to infer absence of an incipient population of brown treesnakes, the approach is sufficiently general to apply to other invasive species if density-dependent detection estimates are known or reliable surrogate estimates are available.

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Section: Methodsmentioning

confidence: 90%

Inferring the absence of an incipient population during a rapid response for an invasive species

et al. 2018

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“…Many studies in Hawai'i (Leopold & Hess, ), and elsewhere in the tropics and subtropics (e.g., Wassie et al, ; Nafus, Adams, Christy, & Reed, ; Nilar et al, ) have found that in ungulate‐disturbed areas, fencing and ungulate removal benefit native plant species communities. They also suggest that the success of passive restoration after fencing and ungulate removal is dependent on the extent to which the area has been degraded.…”

Section: Discussionmentioning

confidence: 99%

“…In probability distribution functions grey areas represent 95% confidence intervals. In bar plots, grey bars represent the average values of null distributions and black segments the 95% confidence intervals IBANEZ ANd HART Many studies in Hawai'i (Leopold & Hess, 2017), and elsewhere in the tropics and subtropics (e.g., Wassie et al, 2009;Nafus, Adams, Christy, & Reed, 2018;Nilar et al, 2019) have found that in ungulate-disturbed areas, fencing and ungulate removal benefit native plant species communities. They also suggest that the success of passive restoration after fencing and ungulate removal is dependent on the extent to which the area has been degraded.…”

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confidence: 99%

Spatial patterns of tree recruitment in a montane Hawaiian wet forest after cattle removal and pig population control

Ibanez¹,

Hart²

2020

Applied Vegetation Science

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Question We measured tree recruitment over approx. 17 to 18 years after cattle removal and pig population control in a Metrosideros polymorpha (Myrtaceae) montane wet forest. We analysed how tree recruitment varies in space and between species. Location Hakalau Forest National Wildlife Refuge, Island of Hawai'i. Methods All woody plants with diameter at breast height ≥5 cm were surveyed twice at approx. 17‐ to 18‐year intervals in 200 circular plots (15‐m radius) located in two sites. We used generalized linear mixed models to analyse how the number of recruits of wind‐ and bird‐dispersed species per plot varied between plots as a function of the number and sizes of remaining trees, grass cover, distance to the forest–grassland edge, and the identity of sites. Within plots, for each species we analysed the density distribution of recruits as a function of a neighbourhood crowding index and grass cover. Observed distributions were compared to null distributions. Results About 4,000 recruits representing seven species were inventoried. Wind‐dispersed species tended to recruit randomly, including in open, grassy areas. The number of bird‐dispersed recruits was negatively associated with grass cover and positively associated with basal area of remaining trees. Bird‐dispersed species recruited more in areas with an intermediate neighbourhood crowding index. The number of recruits was strongly correlated with the number of remaining trees for each species. One species, Cheirodendron trigynum (Araliaceae), recruited twice as much as expected given the number of remnant trees. Conclusions The high levels of recruitment of all species were likely due to cattle removal as well as pig population control. Competition with grasses constitutes the main limiting factor for tree recruitment following removal of ungulates. Remnant Metrosideros polymorpha likely create favourable conditions for the recruitment of bird‐dispersed species. Higher seed production and growth rates likely allowed Cheirodendron trigynum to recruit much more than the other species.

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“…Guam's forests have been acutely damaged by non-native pigs (Sus scrofa L.) descended from introductions in the 1600s [36], and deer (Rusa marianna Desmarest) descended from introductions in the 1700s [37]. Exlosures of these Guam ungulates have revealed restoration can be rapid [38,39], and soil chemical traits are among the important ecological processes that are restored following ungulate exclosure [40,41]. Physical disturbance of the litter and soil is one means by which non-native ungulates damage ecosystem processes such as nutrient cycling [42][43][44][45][46].…”

Section: Case 5 Multiple Approved Practitioners Accessing the Same Cmentioning

confidence: 99%

Tree conservation can be constrained by agents from conservation permitting and funding agencies

Marler

2019

Communicative & Integrative Biology

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Recent conservation actions for Serianthes nelsonii Merr. and Cycas micronesica K.D. Hill in the Mariana Islands have illuminated some negative consequences associated with ill-informed agents representing permitting and funding agencies. Several cases from the islands of Guam and Tinian are discussed as ineffective conservation examples, and these are countered with two examples of successful conservation approaches. When biologists that act as points of contact for federal permitting and funding agencies do not possess education, knowledge, and experience that is germane to federally listed species, sound science may be marginalized from the conservation agenda. When rapid turnover of federal conservation agents introduces dysfunction, discontinuities in collaborations may thwart success. When lapses in conservation contracts are allowed, short-term extemporary contracting approaches are utilized, and conservation practitioners that lack the ability to include an experimental approach to conservation actions are employed, the co-production of new knowledge to enable decision support tools for future decision-makers may be hindered.

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Passive restoration following ungulate removal in a highly disturbed tropical wet forest devoid of native seed dispersers

Cited by 9 publications

References 27 publications

Inferring the absence of an incipient population during a rapid response for an invasive species

Inferring the absence of an incipient population during a rapid response for an invasive species

Spatial patterns of tree recruitment in a montane Hawaiian wet forest after cattle removal and pig population control

Tree conservation can be constrained by agents from conservation permitting and funding agencies

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