ORCID Profile
0000-0003-2256-6649
Current Organisation
CORDIO East Africa
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Research Square Platform LLC
Date: 06-06-2022
DOI: 10.21203/RS.3.RS-1555992/V1
Abstract: Ocean warming is increasing the incidence, scale, and severity of global-scale coral bleaching and mortality, culminating in the third global coral bleaching event that occurred during record marine heatwaves of 2014-2017. While local effects of these events have been widely reported, the global implications remain unknown. Analysis of 15,066 reef surveys during 2014-2017 revealed that 80% of surveyed reefs experienced significant coral bleaching and 35% experienced significant coral mortality. The global extent of significant coral bleaching and mortality was assessed by extrapolating results from reef surveys using comprehensive remote-sensing data of regional heat stress. This model predicted that 51% of the world’s coral reefs suffered significant bleaching and 15% significant mortality, surpassing damage from any prior global bleaching event. These observations demonstrate that global warming’s widespread damage to coral reefs is accelerating and underscores the threat anthropogenic climate change poses for the irreversible transformation of these essential ecosystems.
Publisher: Elsevier BV
Date: 02-2023
Publisher: Springer Science and Business Media LLC
Date: 31-05-2023
DOI: 10.1038/S41586-023-06083-8
Abstract: The stability and resilience of the Earth system and human well-being are inseparably linked 1–3 , yet their interdependencies are generally under-recognized consequently, they are often treated independently 4,5 . Here, we use modelling and literature assessment to quantify safe and just Earth system boundaries (ESBs) for climate, the biosphere, water and nutrient cycles, and aerosols at global and subglobal scales. We propose ESBs for maintaining the resilience and stability of the Earth system (safe ESBs) and minimizing exposure to significant harm to humans from Earth system change (a necessary but not sufficient condition for justice) 4 . The stricter of the safe or just boundaries sets the integrated safe and just ESB. Our findings show that justice considerations constrain the integrated ESBs more than safety considerations for climate and atmospheric aerosol loading. Seven of eight globally quantified safe and just ESBs and at least two regional safe and just ESBs in over half of global land area are already exceeded. We propose that our assessment provides a quantitative foundation for safeguarding the global commons for all people now and into the future.
Publisher: Springer Science and Business Media LLC
Date: 16-08-2021
Publisher: Springer Science and Business Media LLC
Date: 06-12-2021
DOI: 10.1038/S41893-021-00817-0
Abstract: Ecosystems worldwide are under increasing threat. We applied a standardized method for assessing the risk of ecosystem collapse, the International Union for Conservation of Nature (IUCN) Red List of Ecosystems, to coral reefs in the Western Indian Ocean (WIO), covering 11,919 km 2 of reef (~5% of the global total). Our approach combined indicators of change in historic ecosystem extent, ecosystem functioning (hard corals, fleshy algae, herbivores and piscivores) and projected sea temperature warming. We show that WIO coral reefs are vulnerable to collapse at the regional level, while in 11 nested ecoregions they range from critically endangered (islands, driven by future warming) to vulnerable (continental coast and northern Seychelles, driven principally by fishing pressure). Responses to avoid coral reef collapse must include ecosystem-based management of reefs and adjacent systems combined with mitigating and adapting to climate change. Our approach can be replicated across coral reefs globally to help countries and other actors meet conservation and sustainability targets set under multiple global conventions—including the Convention on Biological Diversity’s post-2020 global bio ersity framework and the United Nations’ Sustainable Development Goals.
Publisher: Cold Spring Harbor Laboratory
Date: 27-06-2022
DOI: 10.1101/2022.06.24.497294
Abstract: Defining a safe and just biosphere space requires a synthetic scaleable measure of biosphere functional integrity to secure Nature’s Contributions to People (NCP). Using a systematic review of 153 peer-reviewed studies we estimated the minimum level of functional integrity needed to secure multiple critical NCP, including pollination, pest and disease control, water quality regulation, soil protection, recreation and natural hazards mitigation in human-modified landscapes. We characterise functional integrity by the quantity, quality and spatial configuration of (semi-)natural habitat within any landscape. We find that at least 20-25% of structurally complex and biologically erse (semi-)natural habitat in each 1 km 2 of land area is needed to maintain the supply of multiple NCP simultaneously. Exact quantity, quality and spatial configuration required is dependent on local context, and may differ for in idual NCP. Today, about 50-60% of human-modified lands have less than 10% and 20% (semi-)natural habitat per 1 km 2 respectively. These areas require immediate attention to regenerate functional integrity in order to secure ecological functioning in those landscapes.
Publisher: Springer Science and Business Media LLC
Date: 07-07-2022
DOI: 10.1038/S41559-022-01812-0
Abstract: The bio ersity of marine and coastal habitats is experiencing unprecedented change. While there are well-known drivers of these changes, such as overexploitation, climate change and pollution, there are also relatively unknown emerging issues that are poorly understood or recognized that have potentially positive or negative impacts on marine and coastal ecosystems. In this inaugural Marine and Coastal Horizon Scan, we brought together 30 scientists, policymakers and practitioners with transdisciplinary expertise in marine and coastal systems to identify new issues that are likely to have a significant impact on the functioning and conservation of marine and coastal bio ersity over the next 5-10 years. Based on a modified Delphi voting process, the final 15 issues presented were distilled from a list of 75 submitted by participants at the start of the process. These issues are grouped into three categories: ecosystem impacts, for ex le the impact of wildfires and the effect of poleward migration on equatorial bio ersity resource exploitation, including an increase in the trade of fish swim bladders and increased exploitation of marine collagens and new technologies, such as soft robotics and new biodegradable products. Our early identification of these issues and their potential impacts on marine and coastal bio ersity will support scientists, conservationists, resource managers and policymakers to address the challenges facing marine ecosystems.
Publisher: Public Library of Science (PLoS)
Date: 03-06-2010
Publisher: Springer Science and Business Media LLC
Date: 25-03-2010
Publisher: Public Library of Science (PLoS)
Date: 02-05-2012
Publisher: Inter-Research Science Center
Date: 25-10-2007
DOI: 10.3354/MEPS07090
Publisher: Research Square Platform LLC
Date: 02-05-2023
DOI: 10.21203/RS.3.RS-2861426/V1
Abstract: Safe and just Earth System Boundaries (ESBs) for surface and groundwater (blue water) have been defined for sustainable water management in the Anthropocene. We evaluate where minimum human needs can be met within the surface water ESB and, where this is not possible, identify how much groundwater is required. 2.6 billion people live in catchments where groundwater is needed because they are already outside the surface water ESB or have insufficient surface water to meet human needs and the ESB. Approximately 1.4 billion people live in catchments where demand side transformations are required as they either exceed the surface water ESB or face a decline in groundwater recharge and cannot meet minimum needs within the ESB. A further 1.5 billion people live in catchments outside the ESB with insufficient surface water to meet needs, requiring both supply and demand-side transformations. These results highlight the challenges and opportunities of meeting even basic human access needs to water and protecting aquatic ecosystems.
Publisher: Springer Science and Business Media LLC
Date: 20-06-2022
Publisher: International Coral Reef Society and Future Earth Coasts
Date: 20-07-2021
DOI: 10.53642/NRKY9386
Abstract: This document is the work of a team assembled by the International Coral Reef Society (ICRS). The mission of ICRS is to promote the acquisition and dissemination of scientific knowledge to secure the future of coral reefs, including via relevant policy frameworks and decision-making processes. This document seeks to highlight the urgency of taking action to conserve and restore reefs through protection and management measures, to provide a summary of the most relevant and recent natural and social science that provides guidance on these tasks, and to highlight implications of these findings for the numerous discussions and negotiations taking place at the global level.
Publisher: American Geophysical Union (AGU)
Date: 30-08-2021
DOI: 10.1029/2021GL094128
Abstract: Ocean warming is causing declines of coral reefs globally, raising critical questions about the potential for corals to adapt. In the central equatorial Pacific, reefs persisting through recurrent El Niño heatwaves hold important clues. Using an 18‐year record of coral cover spanning three major bleaching events, we show that the impact of thermal stress on coral mortality within the Phoenix Islands Protected Area (PIPA) has lessened over time. Disproportionate survival of extreme thermal stress during the 2009–2010 and 2015–2016 heatwaves, relative to that in 2002–2003, suggests that selective mortality through successive heatwaves may help shape coral community responses to future warming. Identifying and facilitating the conditions under which coral survival and recovery can keep pace with rates of warming are essential first steps toward successful stewardship of coral reefs under 21st century climate change.
Publisher: Springer Science and Business Media LLC
Date: 02-03-2023
Publisher: Wiley
Date: 05-2010
Publisher: American Geophysical Union (AGU)
Date: 04-2021
DOI: 10.1029/2020EF001866
Abstract: Keeping the Earth system in a stable and resilient state, to safeguard Earth's life support systems while ensuring that Earth's benefits, risks, and related responsibilities are equitably shared, constitutes the grand challenge for human development in the Anthropocene. Here, we describe a framework that the recently formed Earth Commission will use to define and quantify target ranges for a “safe and just corridor” that meets these goals. Although “safe” and “just” Earth system targets are interrelated, we see safe as primarily referring to a stable Earth system and just targets as being associated with meeting human needs and reducing exposure to risks. To align safe and just dimensions, we propose to address the equity dimensions of each safe target for Earth system regulating systems and processes. The more stringent of the safe or just target ranges then defines the corridor. Identifying levers of social transformation aimed at meeting the safe and just targets and challenges associated with translating the corridor to actors at multiple scales present scope for future work.
Publisher: Elsevier BV
Date: 10-2009
DOI: 10.1016/J.MARPOLBUL.2009.09.009
Abstract: Temperature-induced mass coral bleaching causing mortality on a wide geographic scale started when atmospheric CO(2) levels exceeded approximately 320 ppm. When CO(2) levels reached approximately 340 ppm, sporadic but highly destructive mass bleaching occurred in most reefs world-wide, often associated with El Niño events. Recovery was dependent on the vulnerability of in idual reef areas and on the reef's previous history and resilience. At today's level of approximately 387 ppm, allowing a lag-time of 10 years for sea temperatures to respond, most reefs world-wide are committed to an irreversible decline. Mass bleaching will in future become annual, departing from the 4 to 7 years return-time of El Niño events. Bleaching will be exacerbated by the effects of degraded water-quality and increased severe weather events. In addition, the progressive onset of ocean acidification will cause reduction of coral growth and retardation of the growth of high magnesium calcite-secreting coralline algae. If CO(2) levels are allowed to reach 450 ppm (due to occur by 2030-2040 at the current rates), reefs will be in rapid and terminal decline world-wide from multiple synergies arising from mass bleaching, ocean acidification, and other environmental impacts. Damage to shallow reef communities will become extensive with consequent reduction of bio ersity followed by extinctions. Reefs will cease to be large-scale nursery grounds for fish and will cease to have most of their current value to humanity. There will be knock-on effects to ecosystems associated with reefs, and to other pelagic and benthic ecosystems. Should CO(2) levels reach 600 ppm reefs will be eroding geological structures with populations of surviving biota restricted to refuges. Domino effects will follow, affecting many other marine ecosystems. This is likely to have been the path of great mass extinctions of the past, adding to the case that anthropogenic CO(2) emissions could trigger the Earth's sixth mass extinction.
Publisher: Springer Science and Business Media LLC
Date: 13-03-2011
Publisher: Public Library of Science (PLoS)
Date: 27-02-2008
Publisher: Wiley
Date: 17-01-2012
DOI: 10.1002/AQC.1248
Publisher: Springer Science and Business Media LLC
Date: 24-08-2023
Publisher: American Association for the Advancement of Science (AAAS)
Date: 18-01-2013
Abstract: A global system of harmonized observations is needed to inform scientists and policy-makers.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 21-04-2023
Abstract: Earth’s bio ersity and human societies face pollution, overconsumption of natural resources, urbanization, demographic shifts, social and economic inequalities, and habitat loss, many of which are exacerbated by climate change. Here, we review links among climate, bio ersity, and society and develop a roadmap toward sustainability. These include limiting warming to 1.5°C and effectively conserving and restoring functional ecosystems on 30 to 50% of land, freshwater, and ocean “scapes.” We envision a mosaic of interconnected protected and shared spaces, including intensively used spaces, to strengthen self-sustaining bio ersity, the capacity of people and nature to adapt to and mitigate climate change, and nature’s contributions to people. Fostering interlinked human, ecosystem, and planetary health for a livable future urgently requires bold implementation of transformative policy interventions through interconnected institutions, governance, and social systems from local to global levels.
Publisher: African Journals Online (AJOL)
Date: 27-07-2023
Abstract: Data on coral reef health prior to large-scale disturbances are unavailable in most parts of the world including the Western Indian Ocean (WIO). Robust coral reef health baselines could improve the understanding of changes occurring to reefs in the 21st century and prevent the “shifting baseline” phenomenon, enabling researchers and managers to evaluate the success of management measures, and set achievable targets for new interventions. To make this data accessible to the WIO coral reef community, a literature review was conducted to identify and compile data collected prior to 2008 for two principal measures of reef health hard coral and fleshy algae cover. Baseline hard coral and algae cover levels were calculated using data from selected sites that were known to be in healthy condition prior to (or just after) the 1998 bleaching event. Mayotte had the highest mean hard coral cover with 80.9 % (95 % bootstrap confidence interval (95 % CI) =65.8-95.9 %), followed by Comoros with 62.1 % (95 % CI=53.2-78.8 %) and Madagascar with 55.6 % (95 % CI=49.8-62.5 %). Mean fleshy algae cover varied from 8.4 % in Mayotte (95 % CI=2.4-17.4 %) to 35.4 % in Mozambique (95 % CI=20.6-50.8 %). At a regional scale, mean baseline hard coral cover is estimated to be between 41 and 47 % reefs were in a coral-dominant state, with more than double the amount of coral compared to algae.
Publisher: Wiley
Date: 05-06-2006
DOI: 10.1111/J.1461-0248.2006.00937.X
Abstract: Declines in coral cover are generally associated with increases in the abundance of fleshy algae. In many cases, it remains unclear whether algae are responsible, directly or indirectly, for coral death or whether they simply settle on dead coral surfaces. Here, we show that algae can indirectly cause coral mortality by enhancing microbial activity via the release of dissolved compounds. When coral and algae were placed in chambers together but separated by a 0.02 mum filter, corals suffered 100% mortality. With the addition of the broad-spectrum antibiotic icillin, mortality was completely prevented. Physiological measurements showed complementary patterns of increasing coral stress with proximity to algae. Our results suggest that as human impacts increase and algae become more abundant on reefs a positive feedback loop may be created whereby compounds released by algae enhance microbial activity on live coral surfaces causing mortality of corals and further algal growth.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 13-12-2019
Abstract: For decades, scientists have been raising calls for societal changes that will reduce our impacts on nature. Though much conservation has occurred, our natural environment continues to decline under the weight of our consumption. Humanity depends directly on the output of nature thus, this decline will affect us, just as it does the other species with which we share this world. Díaz et al. review the findings of the largest assessment of the state of nature conducted as of yet. They report that the state of nature, and the state of the equitable distribution of nature's support, is in serious decline. Only immediate transformation of global business-as-usual economies and operations will sustain nature as we know it, and us, into the future. Science , this issue p. eaax3100
Publisher: Springer Science and Business Media LLC
Date: 09-2011
No related grants have been discovered for David Obura.