Strong seedling recruitment does not limit mangrove vulnerability to harvest
Ecological studies on the impacts of timber harvesting contributed to inform sustainable management strategies of tropical forests. However, these studies rely strongly on two major assumptions: (i) strong seedlings recruitment predispose for positive population dynamics, and (ii) more adult trees i...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2019-01-01
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| Series: | Environmental Research Letters |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1748-9326/ab1def |
| _version_ | 1797747976837267456 |
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| author | Orou G Gaoue Kowiyou Yessoufou |
| author_facet | Orou G Gaoue Kowiyou Yessoufou |
| author_sort | Orou G Gaoue |
| collection | DOAJ |
| description | Ecological studies on the impacts of timber harvesting contributed to inform sustainable management strategies of tropical forests. However, these studies rely strongly on two major assumptions: (i) strong seedlings recruitment predispose for positive population dynamics, and (ii) more adult trees is a guarantee for a strong reproductive capability of the population. These assumptions are applied without accounting for the life history of the harvested species. Here, we revisit these assumptions in light of the life history theory, which predicts different responses of short- and long-lived species to perturbation. We predict that harvesting adults, rather than reducing seedling recruitment of long-lived species, would have greater impact on population dynamics. We tested our prediction on three mangrove species in South Africa. First, we reconstructed the projection matrices for three mangrove species in the Mngazana Estuary of Eastern Cape province of South Africa. Next, we simulated a range of harvest intensities for different life stages and explored how harvesting influences population dynamics. Finally, we examined the age-specific mortality trajectories for all three species. We found that populations of all three species were closer to their stable stage distribution. Contrary to popular belief, we found that changes in seedling recruitment will have minimal effects on mangrove long-term population dynamics, a finding consistent with the life history theory. However, contrary to expectation, simulating harvest of adults had minimal effect on population dynamics. This is due to low reproductive values for these late stages. Our analysis of age-specific mortality trajectories further provided evidence for positive senescence particularly for Avicennia which was the least resilient to harvest. Our findings cast doubt on the traditional forest management strategies that rely strongly on seedling density as a metric of sustainability and forbid unquestionably harvesting large individuals. We call for caution while generalizing forest management strategies irrespective of the life history of the species at hand. |
| first_indexed | 2024-03-12T15:58:19Z |
| format | Article |
| id | doaj.art-182937c4817a4cd798547a9a27bbb6ff |
| institution | Directory Open Access Journal |
| issn | 1748-9326 |
| language | English |
| last_indexed | 2024-03-12T15:58:19Z |
| publishDate | 2019-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | Environmental Research Letters |
| spelling | doaj.art-182937c4817a4cd798547a9a27bbb6ff2023-08-09T14:44:51ZengIOP PublishingEnvironmental Research Letters1748-93262019-01-0114606401910.1088/1748-9326/ab1defStrong seedling recruitment does not limit mangrove vulnerability to harvestOrou G Gaoue0https://orcid.org/0000-0002-0946-2741Kowiyou Yessoufou1Department of Ecology and Evolutionary Biology, University of Tennessee , Knoxville, TN 37996, United States of America; Faculty of Agronomy, University of Parakou , BP 123, Parakou, Benin; Department of Geography, Environmental Management and Energy Studies, University of Johannesburg , APK Campus, Johannesburg, South Africa; Department of Life and Consumer Sciences, University of South Africa , Florida Campus, Johannesburg, South AfricaDepartment of Geography, Environmental Management and Energy Studies, University of Johannesburg , APK Campus, Johannesburg, South AfricaEcological studies on the impacts of timber harvesting contributed to inform sustainable management strategies of tropical forests. However, these studies rely strongly on two major assumptions: (i) strong seedlings recruitment predispose for positive population dynamics, and (ii) more adult trees is a guarantee for a strong reproductive capability of the population. These assumptions are applied without accounting for the life history of the harvested species. Here, we revisit these assumptions in light of the life history theory, which predicts different responses of short- and long-lived species to perturbation. We predict that harvesting adults, rather than reducing seedling recruitment of long-lived species, would have greater impact on population dynamics. We tested our prediction on three mangrove species in South Africa. First, we reconstructed the projection matrices for three mangrove species in the Mngazana Estuary of Eastern Cape province of South Africa. Next, we simulated a range of harvest intensities for different life stages and explored how harvesting influences population dynamics. Finally, we examined the age-specific mortality trajectories for all three species. We found that populations of all three species were closer to their stable stage distribution. Contrary to popular belief, we found that changes in seedling recruitment will have minimal effects on mangrove long-term population dynamics, a finding consistent with the life history theory. However, contrary to expectation, simulating harvest of adults had minimal effect on population dynamics. This is due to low reproductive values for these late stages. Our analysis of age-specific mortality trajectories further provided evidence for positive senescence particularly for Avicennia which was the least resilient to harvest. Our findings cast doubt on the traditional forest management strategies that rely strongly on seedling density as a metric of sustainability and forbid unquestionably harvesting large individuals. We call for caution while generalizing forest management strategies irrespective of the life history of the species at hand.https://doi.org/10.1088/1748-9326/ab1defmangrovepopulation dynamicsreproductive valuesmatrix projection modelSouth Africaseedling recruitment |
| spellingShingle | Orou G Gaoue Kowiyou Yessoufou Strong seedling recruitment does not limit mangrove vulnerability to harvest Environmental Research Letters mangrove population dynamics reproductive values matrix projection model South Africa seedling recruitment |
| title | Strong seedling recruitment does not limit mangrove vulnerability to harvest |
| title_full | Strong seedling recruitment does not limit mangrove vulnerability to harvest |
| title_fullStr | Strong seedling recruitment does not limit mangrove vulnerability to harvest |
| title_full_unstemmed | Strong seedling recruitment does not limit mangrove vulnerability to harvest |
| title_short | Strong seedling recruitment does not limit mangrove vulnerability to harvest |
| title_sort | strong seedling recruitment does not limit mangrove vulnerability to harvest |
| topic | mangrove population dynamics reproductive values matrix projection model South Africa seedling recruitment |
| url | https://doi.org/10.1088/1748-9326/ab1def |
| work_keys_str_mv | AT orouggaoue strongseedlingrecruitmentdoesnotlimitmangrovevulnerabilitytoharvest AT kowiyouyessoufou strongseedlingrecruitmentdoesnotlimitmangrovevulnerabilitytoharvest |