J. Kairo - Profile on Academia.edu (original) (raw)

Papers by J. Kairo

Turning the Tide: How Blue Carbon and Payments for Ecosystem Services (PES) Might Help Save Mangrove Forests

AMBIO, 2014

In this review paper, we aim to describe the potential for, and the key challenges to, applying P... more In this review paper, we aim to describe the potential for, and the key challenges to, applying PES projects to mangroves. By adopting a &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;carbocentric approach,&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; we show that mangrove forests are strong candidates for PES projects. They are particularly well suited to the generation of carbon credits because of their unrivaled potential as carbon sinks, their resistance and resilience to natural hazards, and their extensive provision of Ecosystem Services other than carbon sequestration, primarily nursery areas for fish, water purification and coastal protection, to the benefit of local communities as well as to the global population. The voluntary carbon market provides opportunities for the development of appropriate protocols and good practice case studies for mangroves at a small scale, and these may influence larger compliance schemes in the future. Mangrove habitats are mostly located in developing countries on communally or state-owned land. This means that issues of national and local governance, land ownership and management, and environmental justice are the main challenges that require careful planning at the early stages of mangrove PES projects to ensure successful outcomes and equitable benefit sharing within local communities.

The disjunct zonation pattern of Avicennia marina (Forsk.) Vierh., frequently ob- served along th... more The disjunct zonation pattern of Avicennia marina (Forsk.) Vierh., frequently ob- served along the Kenyan coast as a landward and a seaward zone, has been studied on a morphological level and complemented with preliminary genetic data. The objective was to describe the two zones in-depth in order to provide a background ecological set- ting that may be used in explanations

Faunal and floral secondary succession in a restored mangrove system in Kenya

Colonization of non-planted mangroves into reforested mangrove stands

Ecology and Restoration of Mangrove Systems in Kenya

Annals of botany, 2014

Successive vascular cambia are involved in the secondary growth of at least 200 woody species fro... more Successive vascular cambia are involved in the secondary growth of at least 200 woody species from >30 plant families. In the mangrove Avicennia these successive cambia are organized in patches, creating stems with non-concentric xylem tissue surrounded by internal phloem tissue. Little is known about radial growth and tree stem dynamics in trees with this type of anatomy. This study aims to (1) clarify the process of secondary growth of Avicennia trees by studying its patchiness; and (2) study the radial increment of Avicennia stems, both temporary and permanent, in relation to local climatic and environmental conditions. A test is made of the hypothesis that patchy radial growth and stem dynamics enable Avicennia trees to better survive conditions of extreme physiological drought. Methods Stem variations were monitored by automatic point dendrometers at four different positions around and along the stem of two Avicennia marina trees in the mangrove forest of Gazi Bay (Kenya) du...

Annals of botany, 2006

Although mangroves have been extensively studied, little is known about their ecological wood ana... more Although mangroves have been extensively studied, little is known about their ecological wood anatomy. This investigation examined the potential use of vessel density as a proxy for soil water salinity in the mangrove species Rhizophora mucronata (Rhizophoraceae) from Kenya. In a time-standardized approach, 50 wood discs from trees growing in six salinity categories were investigated. Vessel densities, and tangential and radial diameters of rainy and dry season wood of one distinct year, at three positions on the stem discs, were measured. A repeated-measures ANOVA with the prevailing salinity was performed. Vessel density showed a significant increase with salinity, supporting its use as a prospective measure of salinity. Interestingly, the negative salinity response of the radial diameter of vessels was less striking, and tangential diameter was constant under the varying environmental conditions. An effect of age or growth rate or the presence of vessel dimorphism could be exclud...

Annals of botany, 2004

The mangrove Rhizophora mucronata has previously been reported to lack annual growth rings, thus ... more The mangrove Rhizophora mucronata has previously been reported to lack annual growth rings, thus barring it from dendrochronological studies. In this study the reported absence of the growth rings was reconsidered and the periodic nature of light and dark brown layers visible on polished stem discs investigated. In addition, the formation of these layers in relation to prevailing environmental conditions, as well as their potential for age determination of the trees, was studied. Trees of known age were collected and a 2.5-year cambial marking experiment was conducted to determine the periodic nature of the visible growth layers. Annual indistinct growth rings were detected in R. mucronata and are defined by a low vessel density earlywood and a high vessel density latewood. The formation of these growth rings and their periodic nature was independent from site-specific environmental conditions in two forests along the Kenyan coast. However, the periodic nature of the rings was serio...

Exploitation of mangrove wood products from a subsistence perspective: a case-study in Mida Creek

Testing mangrove forest structure development and various forest management options in Gazi (Kenya) by combining KiWi individual-based modelling with> 20 years of field data

Ecology and Evolution, 2014

1 Sedimentation results in the creation of new mudflats for mangroves to colonize among other ben... more 1 Sedimentation results in the creation of new mudflats for mangroves to colonize among other benefits. However, large sediment input in mangrove areas may be detrimental to these forests. The dynamics of phenological events of three mangrove tree species (Avicennia marina, Ceriops tagal, and Rhizophora mucronata) were evaluated under experimental sediment burial simulating sedimentation levels of 15, 30, and 45 cm. 2 While there was generally no shift in timing of phenological events with sedimentation, the three mangrove tree species each responded differently to the treatments. 3 Partially buried A. marina trees produced more leaves than the controls during the wet season and less during the dry season. Ceriops tagal on the other hand had higher leaf loss and low replacement rates in the partially buried trees during the first 6 months of the experiment but adapted with time, resulting in either equal or higher leaf emergence rates than the controls. 4 Rhizophora mucronata maintained leaf emergence and loss patterns as the unaffected controls but had a higher fecundity and productivity in the 15-cm sedimentation level. 5 The results suggest that under incidences of large sedimentation events (which could be witnessed as a result of climate change impacts coupled with anthropogenic disturbances), mangrove trees may capitalize on "advantages" associated with terrestrial sediment brought into the biotope, thus maintaining the pattern of phenological events.

A patchy growth via successive and simultaneous cambia: Key to success of the most widespread mangrove species Avicennia marina?

Annals of Botany, 2008

Secondary growth via successive cambia has been intriguing researchers for decades. Insight into ... more Secondary growth via successive cambia has been intriguing researchers for decades. Insight into the mechanism of growth layer formation is, however, limited to the cellular level. The present study aims to clarify secondary growth via successive cambia in the mangrove species Avicennia marina on a macroscopic level, addressing the formation of the growth layer network as a whole. In addition, previously suggested effects of salinity on growth layer formation were reconsidered. A 1-year cambial marking experiment was performed on 80 trees from eight sites in two mangrove forests in Kenya. Environmental (soil water salinity and nutrients, soil texture, inundation frequency) and tree characteristics (diameter, height, leaf area index) were recorded for each site. Both groups of variables were analysed in relation to annual number of growth layers, annual radial increment and average growth layer width of stem discs. Between trees of the same site, the number of growth layers formed during the 1-year study period varied from only part of a growth layer up to four growth layers, and was highly correlated to the corresponding radial increment (0-5 mm year(-1)), even along the different sides of asymmetric stem discs. The radial increment was unrelated to salinity, but the growth layer width decreased with increasing salinity and decreasing tree height. A patchy growth mechanism was proposed, with an optimal growth at distinct moments in time at different positions around the stem circumference. This strategy creates the opportunity to form several growth layers simultaneously, as observed in 14 % of the studied trees, which may optimize tree growth under favourable conditions. Strong evidence was provided for a mainly endogenous trigger controlling cambium differentiation, with an additional influence of current environmental conditions in a trade-off between hydraulic efficiency and mechanical stability.

Marine ecosystems are experiencing unprecedented degradation rates higher than any other ecosyste... more 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 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.

Western Indian Ocean Journal of Marine Science, 2009

Mangrove forests consist of a mosaic of tree cohorts, each having a regeneration history that dep... more Mangrove forests consist of a mosaic of tree cohorts, each having a regeneration history that depends on episodic recruitment of seedlings based on the availability of a "regeneration niche". The aim of this study was to assess seedling population structure in Ceriops tagal natural monospecific stands and one eight-year old reforested stand at Gazi Bay, Kenya, to determine performance in terms of growth and survival over a period of two years. Four natural monospecific stands (two on the western creek designated as site 1 and 2, and two on the eastern creek designated as site 4 and 5) were identified with the reforested stand (on the eastern creek) as site 3. The vegetation structure of these stands and natural regeneration were assessed by Linear Regeneration Sampling. Regeneration Class I (RCI) seedlings of known age were tagged and their growth parameters (diameter, height, leaf production and number of nodes) and survival rates monitored for a period of two years. The reforested stand had the same basal area (2.2 ± 0.1 m 2 ha -1 ) as site 1 (2.1 ± 0.1 m 2 ha -1 ), and the former's mean height was also similar to that of western creek sites (1 and 2), but lower than the eastern creek sites (4 and 5). The western creek sites had the highest seedling mortality (61 % for both) and lowest growth rates recorded over the two year period compared to a mortality of 45 % for the eastern sites. An analysis of seedling growth over the two years as a function of measured environmental factors showed a weak interaction, with height above datum (HAD) and canopy cover showing the highest correlation of only 30 %. The high mortality on the western creek sites may be attributed to harsh environmental conditions due to the limited expanse of the intertidal area of the western creek mangroves compounded with anthropogenic pressure due to its proximity to human settlements. Overall, C. tagal forests at Gazi Bay seem to be more vulnerable to environmental stress because they occur at the upper intertidal area, which limits their long-term structural development. Of the four species common at Gazi, C. tagal is the least structurally developed with very low basal areas and mean heights, which are both important determinants of wood quality. These upper-shore forests therefore require management approaches distinct from those of other species to ensure that their natural regeneration and overall structural development are not unsustainably compromised.

How sustainable is the utilization of mangrove products in peri-urban Mombasa, Kenya?

... Publication Mohamed, MOS, Kairo, JG, Dahdouh-Guebas, F. and Koedam N. 2008. ... Ecologically,... more ... Publication Mohamed, MOS, Kairo, JG, Dahdouh-Guebas, F. and Koedam N. 2008. ... Ecologically, mangroves are spawning grounds for fish, as well as feeding habitats and runways of numerous migratory birds (Nagelkerken et al., 2000; Ellison, 2008a; ...

Spatial macrobenthic variations in a tropical mangrove Bay

Ocean & Coastal Management, 2011

Mangroves in Kenya provide a wide range of valuable services to coastal communities despite their... more Mangroves in Kenya provide a wide range of valuable services to coastal communities despite their relatively small total area. Studies at single sites show reductions in extent and quality caused by extraction for fuel wood and timber and clearance for alternative land use including saltpans, aquaculture, and tourism. Such studies suggest that Kenyan mangroves are likely to conform to the general global trend of declining area but there are no reliable recent estimates of either total mangrove extent or trends in coverage for the country. The total extent of Kenyan mangroves was estimated at four points in time (1985, 1992, 2000 and 2010) using Landsat satellite imagery. Due to its medium resolution, Landsat may underestimate mangrove areas in Kenya where relatively small, linear, coastal features occur. There is also a high frequency of clouds in the coastal areas which can cause data gaps during analysis. However comparison with aerial photographs taken in 1992 showed satisfactory levels of accuracy (87.5%) and Cohen's Kappa (0.54) validating its use in this context. These 1992 data provided an independently validated baseline from which to detect changes (fore-and hind-casted) in other periods after removing cloud coverage. We estimated total mangrove coverage in 2010 at 45,590 ha representing a loss of 18% (0.7% yr À1 ) in the 25 years between 1985 and 2010. Rates of mangrove loss for Kenya varied both spatially and temporally with variations possibly due to legislative inadequacies and differences in habitat alteration patterns. Hence freely available Landsat images proved adequate to detect changes in mangroves and revealed that Kenya shows rates of decline similar to (although slower than) global estimates.

Success rates of recruited tree species and their contribution to the structural development of reforested mangrove stands

Marine Ecology Progress Series, 2006

... MATERIALS AND METHODS Study site. This study was conducted at Gazi Bay (Fig. 1) on the southe... more ... MATERIALS AND METHODS Study site. This study was conducted at Gazi Bay (Fig. 1) on the southern coast of Kenya in 2 mono-specific reforested mangrove stands (Sonneratia alba J. Smith and Rhizophora mucronata Lamk), which were both 8 yr old. ... Floristic composition. ...

Marine Ecology Progress Series, 2008

We studied the vegetation structure dynamics of mangroves, in order to contribute to an overall v... more We studied the vegetation structure dynamics of mangroves, in order to contribute to an overall view on the conditions of propagule establishment from the moment they detach from the parental tree. Microtopographical measurements, quantitative data on vegetation, and propagule counts were collected in Gazi Bay (Kenya) and utilized in a 'geographical information systems' (GIS) environment where all modelling took place based on digital terrain modelling (DTM). Suitability maps were created for propagules of Rhizophora mucronata and Ceriops tagal to analyse the dispersal possibilities (through stranding or self-planting) for the present situation, and for cases of degradation and sea level change. The GIS-analyses take into account the available information derived from the field data, but alterations that go hand in hand with degradation and/or sea level changes (e.g. erosion patterns, rates of sediment supply, wave action) were not considered, since our main focus was the behaviour of propagules. We found that the study area has the potential to successfully rejuvenate at present; however, increasing anthropogenic pressure may have severe consequences on propagule dispersal within this mangrove stand, mainly through the loss of aerial root masses, as these were shown to provide stranding areas for propagules. A relatively modest rise in sea level within a time span of 20 yr could affect the distribution pattern and the specific proportion of the juvenile vegetation layer, leading to notable floristic modifications from a regional point of view.