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| Titel |
Mangroves in peril: unprecedented degradation rates of peri-urban mangroves in Kenya |
| VerfasserIn |
J. O. Bosire, J. J. Kaino, A. O. Olagoke, L. M. Mwihaki, G. M. Ogendi, J. G. Kairo, U. Berger, D. Macharia |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 10 ; Nr. 11, no. 10 (2014-05-16), S.2623-2634 |
| Datensatznummer |
250117413
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| Publikation (Nr.) |
 copernicus.org/bg-11-2623-2014.pdf |
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| Zusammenfassung |
| Marine ecosystems are experiencing unprecedented degradation rates higher
than any other ecosystem on the planet, which in some instances are up to
4 times those of rainforests. Mangrove ecosystems have especially been
impacted by compounded anthropogenic pressures leading to significant cover
reductions of between 35 and 50% (equivalent to 1–2% loss pa) for
the last half century. The main objective of this study was to test the
hypothesis that peri-urban mangroves suffering from compounded and intense
pressures may be experiencing higher degradation rates than the global mean
(and/or national mean for Kenya) using Mombasa mangroves (comprising Tudor
and Mwache creeks) as a case study. Stratified sampling was used to sample
along 22 and 10 belt transects in Mwache and Tudor respectively, set to
capture stand heterogeneity in terms of species composition and structure in
addition to perceived human pressure gradients using proximity to human
habitations as a proxy. We acquired SPOT (HRV/ HRVIR/ HRS) images of April
1994, May 2000 and January 2009 and a vector mangrove map of 1992 at a scale
of 1:50 000 for cover change and species composition analysis. Results
from image classification of the 2009 image had 80.23% overall accuracy
and Cohen's kappa of 0.77, thus proving satisfactory for use in this context.
Structural data indicate that complexity index (CI) which captures stand
structural development was higher in Mwache at 1.80 compared to Tudor at
1.71. From cover change data, Tudor lost 86.9% of the forest between
1992 and 2009, compared to Mwache at 45.4%, representing very high
hitherto undocumented degradation rates of 5.1 and 2.7% pa,
respectively. These unprecedentedly high degradation rates, which far exceed
not only the national mean (for Kenya of 0.7% pa) but the global mean
as well, strongly suggest that these mangroves are highly threatened due to
compounded pressures. Strengthening of governance regimes through enforcement
and compliance to halt illegal wood extraction, improvement of land-use
practices upstream to reduce soil erosion, restoration in areas where natural
regeneration has been impaired, provision of alternative energy
sources/building materials and a complete moratorium on wood extraction
especially in Tudor Creek to allow recovery are some of the suggested
management interventions. |
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