Impact of climate change on Indian forests: a dynamic vegetation modeling approach

We make an assessment of the impact of projected climate change on forest ecosystems in India. This assessment is based on climate projections of the Regional Climate Model of the Hadley Centre (HadRM3) and the dynamic global vegetation model IBIS for A2 and B2 scenarios. According to the model projections, 39% of forest grids are likely to undergo vegetation type change under the A2 scenario and 34% under the B2 scenario by the end of this century. However, in many forest dominant states such as Chattisgarh, Karnataka and Andhra Pradesh up to 73%, 67% and 62% of forested grids are projected to undergo change. Net Primary Productivity (NPP) is projected to increase by 68.8% and 51.2% under the A2 and B2 scenarios, respectively, and soil organic carbon (SOC) by 37.5% for A2 and 30.2% for B2 scenario. Based on the dynamic global vegetation modeling, we present a forest vulnerability index for India which is based on the observed datasets of forest density, forest biodiversity as well as model predicted vegetation type shift estimates for forested grids. The vulnerability index suggests that upper Himalayas, northern and central parts of Western Ghats and parts of central India are most vulnerable to projected impacts of climate change, while Northeastern forests are more resilient. Thus our study points to the need for developing and implementing adaptation strategies to reduce vulnerability of forests to projected climate change.     

Building regional priorities in forests for development and adaptation to climate change in the Congo Basin

Indentifying common priorities in shared natural resource systems constitutes an important platform for implementing adaptation and a major step in sharing a common responsibility in addressing climate change. Predominated by discourses on REDD + (Reduced Emissions from Deforestation and Forest Degradation and conservation, sustainable management of forests and enhancement of forest carbon stocks in developing countries) with little emphasis on adaptation there is a risk of lack of policy measures in addressing climate change in the Congo Basin. Forest products and ecosystem services provide security portfolios for the predominantly rural communities, and play major roles in national development programmes in both revenue and employment opportunities. Thus, raising the profile of forests in the policy arena especially in the twin roles of addressing climate change in mitigation and adaptation and achieving resilient development is crucial. Within the framework of the Congo Basin Forests and Climate Change Adaptation project (COFCCA) project, science policy dialogue was conducted to identify and prioritize forest based sectors vulnerable to climate change but important to household livelihoods and national development. The goal of the prioritization process was for the development of intervention in forest as measures for climate change adaptation in Central Africa. Participants constituted a wide range of stakeholders (government, Non Governmental Organizations, research institutions, universities, community leaders, private sectors etc.) as representatives from three countries directly involved in the project: Cameroon, Central African Republic and Democratic Republic of Congo. Building on national priorities, four forest related sectors were identified as common priorities at the regional level for focus on climate change adaptation. These sectors included: (1) energy with emphasis on fuel wood and Charcoal; (2) Water principally quality, quantity, accessibility, etc.; (3) Food with emphasis on Non Timber Forest Products, and (4) Health linked to healthcare products (medicinal plants). Using these prioritized sectors, the project focused on addressing the impacts of climate change on local communities and the development of adaptation strategies in the three pilot countries of the Congo Basin region. The four sectors constitute the key for development in the region and equally considered as priority sectors in the poverty reduction papers. Focused research on these sectors can help to inject the role of forests in national and local development and their potentials contributions to climate change adaptation in national and public discourses. Mainstreaming forest for climate change adaptation into national development planning is the key to improve policy coherence and effectiveness in forest management in the region.     

Profiling climate change vulnerability of forest indigenous communities in the Congo Basin

The livelihood strategies of indigenous communities in the Congo Basin are inseparable from the forests, following their use of forest ecosystem goods and services (FEGS). Climate change is expected to exert impacts on the forest and its ability to provide FEGS. Thus, human livelihoods that depend on these FEGS are intricately vulnerable to climate impacts. Using the livelihood strategies of the two main forest indigenous groups; the Bantus and Pygmies, of the high forest zone of southern Cameroon; this paper examines the nature and pattern of their vulnerability to different climate risks as well as highlights how place of settlement in the forest contributes to the vulnerability of people in forest systems. Forests provide different capitals as FEGS and make direct and indirect contributions to livelihoods which are exploited differently by the two indigenous groups. The results show that vulnerability of forest communities is structured by lifestyle, culture and the livelihood strategies employed which are largely shaped by the place of settlement in the forest. The Pygmies living within the forests are engaged in nomadic gathering and foraging of non-timber forest resources. The Bantus prefer forest margins and are mostly preoccupied with sedentary farming, using the forest as additional livelihood opportunity. The contrasting lifestyles have implications on their vulnerability and adaptation to climate impacts which need to be taken into considerations in planning and implementation of national climate change adaptation strategies.     

Vulnerability of agro-ecological zones in India under the earth system climate model scenarios

India being a developing economy dependent on climate-sensitive sector like agriculture is highly vulnerable to impacts of global climate change. Vulnerability to climate change, however, differs spatially within the country owing to regional differences in exposure, sensitivity, and adaptive capacity. The study uses the Hadley Centre Global Environment Model version 2-Earth System (HadGEM-ES) climate projections to assess the dynamics in vulnerability across four climate change exposure scenarios developed using Representative Concentration Pathways (RCPs). The analysis was carried out at subnational (district) level; the results were interpreted and reported for their corresponding agro-ecological zones. Vulnerability of each district was quantified using indicators capturing climatic variability, ecological and demographic sensitivity, and socio-economic capacity. Our analysis further assigns probabilities to vulnerability classes of all the 579 districts falling under different agro-ecological zones. The results of the vulnerability profile show that Western plains, Northern plains, and central highlands of the arid and semi-arid agro-ecological zones are the most vulnerable regions in the current scenario (1950–2000). In the future scenario (2050), it extends along districts falling within Deccan plateau and Central (Malwa) highlands, lying in the arid and semi-arid zones, along with regions vulnerable in the current scenario, recording the highest vulnerability score across all exposure scenarios. These regions exhibit highest degree of variation in climatic parameters, ecological fragility, socio-economic marginality, and limited accessibility to resources, generating conditions of high vulnerability. The study emphasizes on the priority to take up adaptive management actions in the identified vulnerable districts to not only reduce risks of climate change, but also enhance their inherent capacity to withstand any future changes in climate. It provides a systematic approach to explicitly identify vulnerable regions, where regional planners and policy makers can build on existing adaptation decision-making by utilizing an interdisciplinary approach in the context of global change scenario.     

Land use and climate change adaptation strategies in Kenya

Climate variability and change mitigation and adaptation policies need to prioritize land users needs at local level because it is at this level that impact is felt most. In order to address the challenge of socio-economic and unique regional geographical setting, a customized methodological framework was developed for application in assessment of climate change vulnerability perception and adaptation options around the East African region. Indicators of climate change and variability most appropriate for the region were derived from focused discussions involving key informants in various sectors of the economy drawn from three East African countries. Using these indicators, a structured questionnaire was developed from which surveys and interviews were done on selected sample of target population of farming communities in the Mt. Kenya region. The key highlights of the questionnaire were vulnerability and adaptation. Data obtained from respondents was standardized and subjected to multivariate and ANOVA analysis. Based on principle component analysis (PCA), two main vulnerability categories were identified namely the social and the bio-physical vulnerability indicators. Analysis of variance using Kruskal-Wallis test showed significant statistical variation (P ≤ 0.05) in the perceived vulnerability across the spatial distribution of the 198 respondents. Three insights were distinguished and were discernible by agro-ecological zones. Different vulnerability profiles and adaptive capacity profiles were generated demonstrating the need for prioritizing adaptation and mitigation efforts at local level. There was a high correlation between the bio-physical and social factor/livelihood variables that were assessed.     

Maximising synergies between disaster risk reduction and climate change adaptation: Potential enablers for improved planning outcomes

Recent extreme weather events worldwide have highlighted the vulnerability of many urban settlements to future climatic change. These events are expected to increase in frequency and intensity under climate change scenarios. Although the climatic change may be unavoidable, effective planning and response can reduce its impacts. Drawing on empirical data from a 3-year multi-sectoral study of climate change adaptation for human settlements in the South East Queensland region, Australia, this paper draws on multi-sectoral perspectives to propose enablers for maximising synergies between disaster risk reduction and climate change adaptation to achieve improved planning outcomes. Multi-sectoral perspectives are discussed under four groups of identified enablers: spatial planning; cross-sectoral planning; social/community planning; and strategic/long term planning. Based on the findings, a framework is proposed to guide planning systems to maximise synergies between the fields of disaster risk reduction and climate change adaptation to minimise the vulnerability of communities to extreme weather events in highly urbanised areas.     

Assessment of inherent vulnerability of forests at landscape level: a case study from Western Ghats in India

Assessment of vulnerability is an important step in building long-term resilience in the forestry sector. The objective of this paper is to present a methodological approach to assess inherent vulnerability of forests at landscape level. The approach involves use of vulnerability indicators, the pairwise comparison method, and geographic information system (GIS) tools. We apply this approach to assess the inherent vulnerability of forests of the Western Ghats Karnataka (WGK) landscape, which is a part of the Western Ghats biodiversity hotspot in India. Four vulnerability indicators, namely biological richness, disturbance index, canopy cover, and slope, are selected. We find that forests in 30, 36, 19, and 15 % grid points in this region show low, medium, high, and very high inherent vulnerability, respectively. The forest showing high and very high inherent vulnerability are mostly dry deciduous forests and plantations located largely on the eastern side of the landscape. We also find that canopy cover is one of the key indicators that determine the inherent vulnerability of forests, and natural forests are inherently less vulnerable than man-made plantations. Spatial assessment of inherent vulnerability of forests at landscape level is particularly useful for developing strategies to build resilience to current stressors and climate change in future.     

Socio-economic impacts of climate change on rural United States

Directly or indirectly, positively or negatively, climate change will affect all sectors and regions of the United States. The impacts, however, will not be homogenous across regions, sectors, population groups or time. The literature specifically related to how climate change will affect rural communities, their resilience, and adaptive capacity in the United States (U.S.) is scarce. This article bridges this knowledge gap through an extensive review of the current state of knowledge to make inferences about the rural communities vulnerability to climate change based on Intergovernmental Panel on Climate Change (IPCC) scenarios. Our analysis shows that rural communities tend to be more vulnerable than their urban counterparts due to factors such as demography, occupations, earnings, literacy, poverty incidence, and dependency on government funds. Climate change impacts on rural communities differs across regions and economic sectors; some will likely benefit while others lose. Rural communities engaged in agricultural and forest related activities in the Northeast might benefit, while those in the Southwest and Southeast could face additional water stress and increased energy cost respectively. Developing adaptation and mitigation policy options geared towards reducing climatic vulnerability of rural communities is warranted. A set of regional and local studies is needed to delineate climate change impacts across rural and urban communities, and to develop appropriate policies to mitigate these impacts. Integrating research across disciplines, strengthening research-policy linkages, integrating ecosystem services while undertaking resource valuation, and expanding alternative energy sources, might also enhance coping capacity of rural communities in face of future climate change.     

全球变化下的适应性及其研究进展

全球变化及其相关的适应性研究是当前地学领域研究的焦点问题之一。在综述国内外相关研究成果的基础上,辨析全球变化、适应性等相关概念,梳理适应性研究的发展进程和侧重点,将其归纳为依附脆弱性研究和独立研究两大类。其中,依附脆弱性研究将脆弱性看作是适应能力的函数,研究主要集中在脆弱性评价下的适应指数研究、影响子因素分层研究与策略研究等几大部分;而独立适应性研究,通过构建完整的体系,研究集中在以指标评价法为代表的适应能力研究和以情景模拟法为代表的适应策略预测分析上。地学研究强调适应性的尺度问题,未来需加强对不同尺度规模适应性研究的定量分析,建立跨尺度适应性研究框架;深入研究城市适应全球变化的能力与策略;同时加强适应性研究相关技术和工具的开发,以提高适应能力评估的准确性及适应策略的科学性。     

The rains are disappointing us: dynamic vulnerability and adaptation to multiple stressors in the Afram Plains, Ghana

This paper builds on work on the dynamics of vulnerability and multiple stressors through a case study in the Afram Plains of the Eastern region in Ghana. A vulnerability framework is applied in the community of Mimkyemfre to identify and explain the multiple underlying political, socioeconomic and environmental forces that influence the ways in which people are exposed and sensitive to climate, and their capacities to adapt to changing conditions. The results of the study indicate that the community experiences a range of biophysical and socioeconomic conditions that contribute to its vulnerability. Vulnerability was found to change over time and in some cases was cyclical, in that certain actions taken for the purposes of adaptation were found to exacerbate existing vulnerabilities. Processes of vulnerability were also found to occur at several scales and were experienced unevenly at the community level. The findings of this assessment have important implications for the design and implementation of successful adaptation initiatives, both in Africa and elsewhere. In particular, they demonstrate the need to understand the social, economic and institutional challenges to development as a basis for any contemplation of adaptation to climate change.     

From site-level to regional adaptation planning for tropical commodities: cocoa in West Africa

The production of tropical agricultural commodities, such as cocoa (Theobroma cacao) and coffee (Coffea spp.), the countries and communities engaged in it, and the industries dependent on these commodities, are vulnerable to climate change. This is especially so where a large percentage of the global supply is grown in a single geographical region. Fortunately, there is often considerable spatial heterogeneity in the vulnerability to climate change within affected regions, implying that local production losses could be compensated through intensification and expansion of production elsewhere. However, this requires that site-level actions are integrated into a regional approach to climate change adaptation. We discuss here such a regional approach for cocoa in West Africa, where 70 % of global cocoa supply originates. On the basis of a statistical model of relative climatic suitability calibrated on West African cocoa farming areas and average climate projections for the 2030s and 2050s of, respectively, 15 and 19 Global Circulation Models, we divide the region into three adaptation zones: (i) a little affected zone permitting intensification and/or expansion of cocoa farming; (ii) a moderately affected zone requiring diversification and agronomic adjustments of farming practices; and (iii) a severely affected zone with need for progressive crop change. We argue that for tropical agricultural commodities, larger-scale adaptation planning that attempts to balance production trends across countries and regions could help reduce negative impacts of climate change on regional economies and global commodity supplies, despite the institutional challenges that this integration may pose.     

Forest policies and programs affecting vulnerability and adaptation to climate change

Due to large scale afforestation programs and forest conservation legislations, India’s total forest area seems to have stabilized or even increased. In spite of such efforts, forest fragmentation and degradation continues, with forests being subject to increased pressure due to anthropogenic factors. Such fragmentation and degradation is leading to the forest cover to change from very dense to moderately dense and open forest and 253 km² of very dense forest has been converted to moderately dense forest, open forest, scrub and non-forest (during 2005–2007). Similarly, there has been a degradation of 4,120 km² of moderately dense forest to open forest, scrub and non-forest resulting in a net loss of 936 km² of moderately dense forest. Additionally, 4,335 km² of open forest have degraded to scrub and non-forest. Coupled with pressure due to anthropogenic factors, climate change is likely to be an added stress on forests. Forest sector programs and policies are major factors that determine the status of forests and potentially resilience to projected impacts of climate change. An attempt is made to review the forest policies and programs and their implications for the status of forests and for vulnerability of forests to projected climate change. The study concludes that forest conservation and development policies and programs need to be oriented to incorporate climate change impacts, vulnerability and adaptation.     

Climate change and forests in India: adaptation opportunities and challenges

Climate change is projected to lead to shift of forest types leading to irreversible damage to forests by rendering several species extinct and potentially affecting the livelihoods of local communities and the economy. Approximately 47% and 42% of tropical dry deciduous grids are projected to undergo shifts under A2 and B2 SRES scenarios respectively, as opposed to less than 16% grids comprising of tropical wet evergreen forests. Similarly, the tropical thorny scrub forest is projected to undergo shifts in majority of forested grids under A2 (more than 80%) as well as B2 scenarios (50% of grids). Thus the forest managers and policymakers need to adapt to the ecological as well as the socio-economic impacts of climate change. This requires formulation of effective forest management policies and practices, incorporating climate concerns into long-term forest policy and management plans. India has formulated a large number of innovative and progressive forest policies but a mechanism to ensure effective implementation of these policies is needed. Additional policies and practices may be needed to address the impacts of climate change. This paper discusses an approach and steps involved in the development of an adaptation framework as well as policies, strategies and practices needed for mainstreaming adaptation to cope with projected climate change. Further, the existing barriers which may affect proactive adaptation planning given the scale, accuracy and uncertainty associated with assessing climate change impacts are presented.     

Mitigation and adaptation synergy in forest sector

Mitigation and adaptation are the two main strategies to address climate change. Mitigation and adaptation have been considered separately in the global negotiations as well as literature. There is a realization on the need to explore and promote synergy between mitigation and adaptation while addressing climate change. In this paper, an attempt is made to explore the synergy between mitigation and adaptation by considering forest sector, which on the one hand is projected to be adversely impacted under the projected climate change scenarios and on the other provide opportunities to mitigate climate change. Thus, the potential and need for incorporating adaptation strategies and practices in mitigation projects is presented with a few examples. Firstly, there is a need to ensure that mitigation programs or projects do not increase the vulnerability of forest ecosystems and plantations. Secondly, several adaptation practices could be incorporated into mitigation projects to reduce vulnerability. Further, many of the mitigation projects indeed reduce vulnerability and promote adaptation, for example; forest and biodiversity conservation, protected area management and sustainable forestry. Also, many adaptation options such as urban forestry, soil and water conservation and drought resistant varieties also contribute to mitigation of climate change. Thus, there is need for research and field demonstration of synergy between mitigation and adaptation, so that the cost of addressing climate change impacts can be reduced and co-benefits increased.     

Assessing risk and adaptation options to fires and windstorms in European forestry

Risks can generally be described as the combination of hazard, exposure and vulnerability. Using this framework, we evaluated the historical and future development of risk of fire and wind damage in European forestry at the national level. Fire risk is expected to increase, mainly as a consequence of an increase in fire hazard, defined as the Fire Weather Index in summer. Exposure, defined as forest area, is expected to increase slightly as a consequence of active afforestation and abandonment of marginal agricultural areas. Adaptation options to fire risk should therefore aim to decrease the vulnerability, where a change in tree species from conifers to broadleaves had most effect. Risk for wind damage in forests is expected to increase mainly as a consequence of increase in exposure (total growing stock) and vulnerability (defined by age class and tree species distribution). Projections of future wind climate indicate an increase in hazard (storminess) mainly over Western Europe. Adaptation options should aim to limit the increase in exposure and vulnerability. Only an increase in harvest level can stop the current build-up of growing stock, while at the same time it will lower vulnerability through the reduction of the share of old and vulnerable stands. Changing species from conifers to broadleaves helps to reduce vulnerability as well. Lowering vulnerability by decreasing the rotation length is only effective in combination with a high demand for wood. Due to data limitations, no forecast of future fire area or damaged timber amount by storms was possible.     

A Method for Integrated Assessment of Vulnerability to Climate Change in Siberian Forests: Example of Larch Area

The conceptual scheme of integrated assessment of vulnerability to climate change in Siberian forests is elaborated and applied to the extensive area in Siberia covered by Larch forests. Forest stakeholders on the provincial level are identified to be the most relevant for an integrated impact assessment. Organisation of the assessment study as a combination of 'top-down' and 'bottom-up' approaches is suggested. Major biophysical vulnerability indexes and regional syndromes are identified as the growing stock and current increment averaged by administrative unit. Models and data suitability and quality for an analysis of biophysical vulnerability in conditions of climate change are studied for Siberian forests and future development trends are identified. An application of the elaborated conceptual scheme, which employs two models of different type and forest inventory data, is presented for the Larch area.     

Risks of sea level rise to disadvantaged communities in the United States

Climate change and sea level rise (SLR) pose risks to coastal communities around the world, but societal understanding of the distributional and equity implications of SLR impacts and adaptation actions remains limited. Here, we apply a new analytic tool to identify geographic areas in the contiguous United States that may be more likely to experience disproportionate impacts of SLR, and to determine if and where socially vulnerable populations would bear disproportionate costs of adaptation. We use the Social Vulnerability Index (SoVI) to identify socially vulnerable coastal communities, and combine this with output from a SLR coastal property model that evaluates threats of inundation and the economic efficiency of adaptation approaches to respond to those threats. Results show that under the mid-SLR scenario (66.9 cm by 2100), approximately 1,630,000 people are potentially affected by SLR. Of these, 332,000 (～20%) are among the most socially vulnerable. The analysis also finds that areas of higher social vulnerability are much more likely to be abandoned than protected in response to SLR. This finding is particularly true in the Gulf region of the United States, where over 99% of the most socially vulnerable people live in areas unlikely to be protected from inundation, in stark contrast to the least socially vulnerable group, where only 8% live in areas unlikely to be protected. Our results demonstrate the importance of considering the equity and environmental justice implications of SLR in climate change policy analysis and coastal adaptation planning.     

Analyzing the efficacy of subtropical urban forests in offsetting carbon emissions from cities

Urban forest management and policies have been promoted as a tool to mitigate carbon dioxide (CO₂) emissions. This study used existing CO₂ reduction measures from subtropical Miami-Dade and Gainesville, USA and modeled carbon storage and sequestration by trees to analyze policies that use urban forests to offset carbon emissions. Field data were analyzed, modeled, and spatially analyzed to compare CO₂ sequestered by managing urban forests to equivalent amounts of CO₂ emitted in both urban areas. Urban forests in Gainesville have greater tree density, store more carbon and present lower per-tree sequestration rates than Miami-Dade as a result of environmental conditions and urbanization patterns. Areas characterized by natural pine-oak forests, mangroves, and stands of highly invasive trees were most apt at sequestering CO₂. Results indicate that urban tree sequestration offsets CO₂ emissions and, relative to total city-wide emissions, is moderately effective at 3.4 percent and 1.8 percent in Gainesville and Miami-Dade, respectively. Moreover, converting available non-treed areas into urban forests would not increase overall CO₂ emission reductions substantially. Current CO₂ sequestration by trees was comparable to implemented CO₂ reduction policies. However, long-term objectives, multiple ecosystem services, costs, community needs, and preservation of existing forests should be considered when managing trees for climate change mitigation and other ecosystem services.     

Forests and climate change adaptation policies in Cameroon

Nowadays, adaptation has become a key focus of the scientific and policy-making communities and is a major area of discussion in the multilateral climate change process. As climate change is projected to hit the poorest the hardest, it is especially important for developing countries to pay particular attention to the management of natural resources and agricultural activities. In most of these countries such as Cameroon, forest can play important role in achieving broader climate change adaptation goals. However, forest generally receives very little attention in national development programme and strategies such as policy dialogues on climate change and poverty reduction strategies. Using a qualitative approach to data collection through content analysis of relevant Cameroon policy documents, the integration of climate change adaptation was explored and the level of attention given to forests for adaptation analysed. Results indicate that, with the exception of the First National Communication to UNFCCC that focused mostly on mitigation and related issues, current policy documents in Cameroon are void of tangible reference to climate change, and hence failing in drawing the relevance of forest in sheltering populations from the many projected impacts of climate change. Policies related to forest rely on a generalized concept of sustainable forest management and do not identify the specific changes that need to be incorporated into management strategies and policies towards achieving adaptation. The strategies and recommendations made in those documents only serve to improve understanding of Cameroon natural resources and add resilience to the natural systems in coping with anthropogenic stresses. The paper draws attention to the need to address the constraints of lack of awareness and poor flow of information on the potentials of forests for climate change adaptation. It highlights the need for integrating forest for adaptation into national development programmes and strategies, and recommends a review of the existing environmental legislations and their implications on poverty reduction strategy and adaptation to climate change.     

A global assessment of adaptation investment from the perspectives of equity and efficiency

Equity and efficiency should be considered when allocating resources for climate change adaptation. More than a decade after the Least Developed Countries Fund approved adaptation funds for 18 countries in 2003, it is possible to take the stock of investment data and to test empirically whether equity and efficiency have been factored into adaptation investment decision-making. To evaluate equity, one must determine if resources were distributed to areas of greatest need. Vulnerability assessments provide information on the global distribution of the need for adaptation. To evaluate efficiency, one must compare cost and benefit of an investment. Although it is difficult to assess ex-ante the cost and benefit of investment strategies, it is possible to measure efficient use of expenditures with readiness assessment, as a metric of capacity to deploy adaptation resources. We used vulnerability and readiness measures of the Notre Dame Global Adaptation Initiative (ND-GAIN) Country Index as proxies of equity and efficiency. This article quantitatively interrogates—through the lens of public fund allocation—the roles of vulnerability and readiness in shaping adaptation investment decisions. Our findings suggest that countries facing increasing impacts from climate change have received more adaptation investments from international sources than countries with less vulnerability. Further, international investments also preferentially flow to countries that are more ready to deploy adaptation resources. Since the most vulnerable countries are likely to be less ready for investment, our findings support the efforts to improve the investment potential of the most vulnerable countries by investing first to enhance their readiness, in order to unlock adaptation solutions.