Sub-continental-scale carbon stocks of individual trees in African drylands.

The distribution of dryland trees and their density, cover, size, mass and carbon content are not well known at sub-continental to continental scales1-14. This information is important for ecological protection, carbon accounting, climate mitigation and restoration efforts of dryland ecosystems15-18. We assessed more than 9.9 billion trees derived from more than 300,000 satellite images, covering semi-arid sub-Saharan Africa north of the Equator. We attributed wood, foliage and root carbon to every tree in the 0-1,000 mm year-1 rainfall zone by coupling field data19, machine learning20-22, satellite data and high-performance computing. Average carbon stocks of individual trees ranged from 0.54 Mg C ha-1 and 63 kg C tree-1 in the arid zone to 3.7 Mg C ha-1 and 98 kg tree-1 in the sub-humid zone. Overall, we estimated the total carbon for our study area to be 0.84 (±19.8%) Pg C. Comparisons with 14 previous TRENDY numerical simulation studies23 for our area found that the density and carbon stocks of scattered trees have been underestimated by three models and overestimated by 11 models, respectively. This benchmarking can help understand the carbon cycle and address concerns about land degradation24-29. We make available a linked database of wood mass, foliage mass, root mass and carbon stock of each tree for scientists, policymakers, dryland-restoration practitioners and farmers, who can use it to estimate farmland tree carbon stocks from tablets or laptops.

An unexpectedly large count of trees in the West African Sahara and Sahel.

A large proportion of dryland trees and shrubs (hereafter referred to collectively as trees) grow in isolation, without canopy closure. These non-forest trees have a crucial role in biodiversity, and provide ecosystem services such as carbon storage, food resources and shelter for humans and animals1,2. However, most public interest relating to trees is devoted to forests, and trees outside of forests are not well-documented3. Here we map the crown size of each tree more than 3 m2 in size over a land area that spans 1.3 million km2 in the West African Sahara, Sahel and sub-humid zone, using submetre-resolution satellite imagery and deep learning4. We detected over 1.8 billion individual trees (13.4 trees per hectare), with a median crown size of 12 m2, along a rainfall gradient from 0 to 1,000 mm per year. The canopy cover increases from 0.1% (0.7 trees per hectare) in hyper-arid areas, through 1.6% (9.9 trees per hectare) in arid and 5.6% (30.1 trees per hectare) in semi-arid zones, to 13.3% (47 trees per hectare) in sub-humid areas. Although the overall canopy cover is low, the relatively high density of isolated trees challenges prevailing narratives about dryland desertification5-7, and even the desert shows a surprisingly high tree density. Our assessment suggests a way to monitor trees outside of forests globally, and to explore their role in mitigating degradation, climate change and poverty.

Forest management in southern China generates short term extensive carbon sequestration.

Land use policies have turned southern China into one of the most intensively managed forest regions in the world, with actions maximizing forest cover on soils with marginal agricultural potential while concurrently increasing livelihoods and mitigating climate change. Based on satellite observations, here we show that diverse land use changes in southern China have increased standing aboveground carbon stocks by 0.11 ± 0.05 Pg C y-1 during 2002-2017. Most of this regional carbon sink was contributed by newly established forests (32%), while forests already existing contributed 24%. Forest growth in harvested forest areas contributed 16% and non-forest areas contributed 28% to the carbon sink, while timber harvest was tripled. Soil moisture declined significantly in 8% of the area. We demonstrate that land management in southern China has been removing an amount of carbon equivalent to 33% of regional fossil CO2 emissions during the last 6 years, but forest growth saturation, land competition for food production and soil-water depletion challenge the longevity of this carbon sink service.

Changes in rainfall distribution promote woody foliage production in the Sahel.

Dryland ecosystems comprise a balance between woody and herbaceous vegetation. Climate change impacts rainfall timing, which may alter the respective contributions of woody and herbaceous plants on the total vegetation production. Here, we apply 30 years of field-measured woody foliage and herbaceous mass from Senegal and document a faster increase in woody foliage mass (+17 kg ha-1 yr-1) as compared to herbaceous mass (+3 kg ha-1 yr-1). Annual rainfall trends were partitioned into core wet-season rains (+0.7 mm yr-1), supporting a weak but periodic (5-year cycles) increase in herbaceous mass, and early/late rains (+2.1 mm yr-1), explaining the strongly increased woody foliage mass. Satellite observations confirm these findings for the majority of the Sahel, with total herbaceous/woody foliage mass increases by 6%/20%. We conclude that the rainfall recovery in the Sahel does not benefit herbaceous vegetation to the same extent as woody vegetation, presumably favoured by increased early/late rains.

Satellite passive microwaves reveal recent climate-induced carbon losses in African drylands.

The African continent is facing one of the driest periods in the past three decades as well as continued deforestation. These disturbances threaten vegetation carbon (C) stocks and highlight the need for improved capabilities of monitoring large-scale aboveground carbon stock dynamics. Here we use a satellite dataset based on vegetation optical depth derived from low-frequency passive microwaves (L-VOD) to quantify annual aboveground biomass-carbon changes in sub-Saharan Africa between 2010 and 2016. L-VOD is shown not to saturate over densely vegetated areas. The overall net change in drylands (53% of the land area) was -0.05 petagrams of C per year (Pg C yr-1) associated with drying trends, and a net change of -0.02 Pg C yr-1 was observed in humid areas. These trends reflect a high inter-annual variability with a very dry year in 2015 (net change, -0.69 Pg C) with about half of the gross losses occurring in drylands. This study demonstrates, first, the applicability of L-VOD to monitor the dynamics of carbon loss and gain due to weather variations, and second, the importance of the highly dynamic and vulnerable carbon pool of dryland savannahs for the global carbon balance, despite the relatively low carbon stock per unit area.

"Reduction of tree cover in West African woodlands and promotion in semi-arid farmlands".

Woody vegetation in farmland acts as a carbon sink and provides ecosystem services for local people, but no macro-scale assessments of the impact of management and climate on woody cover exists for drylands. Here we make use of very high spatial resolution satellite imagery to derive wall-to-wall woody cover patterns in tropical West African drylands. Our study reveals a consistently high woody cover in farmlands along all semi-arid and sub-humid rainfall zones (16%), on average only 6% lower than in savannas. In semi-arid Sahel, farmland management increases woody cover to a greater level (12%) than found in neighbouring savannas (6%), whereas farmlands in sub-humid zones have a reduced woody cover (20%) as compared to savannas (30%). In the region as a whole, rainfall, terrain and soil are the most important (80%) determinants of woody cover, while management factors play a smaller (20%) role. We conclude that agricultural expansion cannot generally be claimed to cause woody cover losses, and that observations in Sahel contradict simplistic ideas of a high negative correlation between population density and woody cover.

Human population growth offsets climate-driven increase in woody vegetation in sub-Saharan Africa.

The rapidly growing human population in sub-Saharan Africa generates increasing demand for agricultural land and forest products, which presumably leads to deforestation. Conversely, a greening of African drylands has been reported, but this has been difficult to associate with changes in woody vegetation. There is thus an incomplete understanding of how woody vegetation responds to socio-economic and environmental change. Here we used a passive microwave Earth observation data set to document two different trends in land area with woody cover for 1992-2011: 36% of the land area (6,870,000 km2) had an increase in woody cover largely in drylands, and 11% had a decrease (2,150,000 km2), mostly in humid zones. Increases in woody cover were associated with low population growth, and were driven by increases in CO2 in the humid zones and by increases in precipitation in drylands, whereas decreases in woody cover were associated with high population growth. The spatially distinct pattern of these opposing trends reflects, first, the natural response of vegetation to precipitation and atmospheric CO2, and second, deforestation in humid areas, minor in size but important for ecosystem services, such as biodiversity and carbon stocks. This nuanced picture of changes in woody cover challenges widely held views of a general and ongoing reduction of the woody vegetation in Africa.

Mapping gains and losses in woody vegetation across global tropical drylands.

Woody vegetation in global tropical drylands is of significant importance for both the interannual variability of the carbon cycle and local livelihoods. Satellite observations over the past decades provide a unique way to assess the vegetation long-term dynamics across biomes worldwide. Yet, the actual changes in the woody vegetation are always hidden by interannual fluctuations of the leaf density, because the most widely used remote sensing data are primarily related to the photosynthetically active vegetation components. Here, we quantify the temporal trends of the nonphotosynthetic woody components (i.e., stems and branches) in global tropical drylands during 2000-2012 using the vegetation optical depth (VOD), retrieved from passive microwave observations. This is achieved by a novel method focusing on the dry season period to minimize the influence of herbaceous vegetation and using MODerate resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) data to remove the interannual fluctuations of the woody leaf component. We revealed significant trends (P < 0.05) in the woody component (VODwood ) in 35% of the areas characterized by a nonsignificant trend in the leaf component (VODleaf modeled from NDVI), indicating pronounced gradual growth/decline in woody vegetation not captured by traditional assessments. The method is validated using a unique record of ground measurements from the semiarid Sahel and shows a strong agreement between changes in VODwood and changes in ground observed woody cover (r2  = 0.78). Reliability of the obtained woody component trends is also supported by a review of relevant literatures for eight hot spot regions of change. The proposed approach is expected to contribute to an improved assessment of, for example, changes in dryland carbon pools.

Vietnam's forest transition in retrospect: demonstrating weaknesses in business-as-usual scenarios for REDD.

One of the prerequisites of the REDD+ mechanism is to effectively predict business-as-usual (BAU) scenarios for change in forest cover. This would enable estimation of how much carbon emission a project could potentially prevent and thus how much carbon credit should be rewarded. However, different factors like forest degradation and the lack of linearity in forest cover transitions challenge the accuracy of such scenarios. Here we predict and validate such BAU scenarios retrospectively based on forest cover changes at village and district level in North Central Vietnam. With the government's efforts to increase the forest cover, land use policies led to gradual abandonment of shifting cultivation since the 1990s. We analyzed Landsat images from 1973, 1989, 1998, 2000, and 2011 and found that the policies in the areas studied did lead to increased forest cover after a long period of decline, but that this increase could mainly be attributed to an increase in open forest and shrub areas. We compared Landsat classifications with participatory maps of land cover/use in 1998 and 2012 that indicated more forest degradation than was captured by the Landsat analysis. The BAU scenarios were heavily dependent on which years were chosen for the reference period. This suggests that hypothetical REDD+ activities in the past, when based on the remote sensing data available at that time, would have been unable to correctly estimate changes in carbon stocks and thus produce relevant BAU scenarios.

Transfusion rate and prevalence of unexpected red blood cell alloantibodies in women undergoing hysterectomy for benign disease.

OBJECTIVE: To determine transfusion rates, risk factors for transfusion and the prevalence of unexpected red blood cell alloantibodies in women undergoing hysterectomy for benign disease. In addition, we aimed to evaluate the necessity of the pretransfusion testing for red blood cell alloantibodies. DESIGN: Retrospective cohort study. SETTING: The Danish Hysterectomy Database and a regional computerized blood bank register. POPULATION: The 4 181 hysterectomies in 2004 reported to the Hysterectomy Database. The blood bank registers 2 603 hysterectomies performed between 1997 and 2005. METHODS: From the hysterectomy database, information about indications for the hysterectomy, surgical procedures, re-operations, number of blood transfusions, and demographic, descriptive and clinical characteristics were extracted. Urgency of the transfusion episodes was evaluated by a retrospective review of the patients' medical records. From the regional blood bank register, results of the screening for red blood cell alloantibodies were extracted. MAIN OUTCOME MEASURES: Transfusion rates, prevalence of unexpected red blood cell alloantibodies. RESULTS: In all, 242 women (5.8%) received blood transfusions, but only 32 of the 4 181 women (0.77%) were urgently transfused. Re-operations were frequently associated with urgent blood transfusions. Nine of the 2 603 women from the regional register (0.35%) had newly detected, clinically significant red blood cell alloantibodies. CONCLUSIONS: The risk of a hemolytic transfusion reaction was estimated to be less than 1 in 17 000 hysterectomies (upper confidence limit) if the routine pretransfusion test were to be omitted. We suggest that reconsideration of the necessity for routine preoperative pretransfusion testing for women undergoing hysterectomy for benign disease is indicated.

No change in adolescents' neglect on contraceptive use over two decades.

PURPOSE: The sexual activity and contraceptive use is evaluated over 21 years amongst Danish adolescents in ninth grade. METHODS: A repeated, cross-sectional questionnaire study in the municipality of Viborg, comparing the results of four consecutive surveys between 1986 and 2007. RESULTS: In 2007, 40% of the pupils had sexual debut at an average age of 15.3 ± 1.5 years. At sexual debut condoms were used in 77% of the adolescents and the contraceptive pill in 15%. At their latest coitus 34% used any contraceptive pill as 27% of pupils changed from use of condom to the pill. Practical experience with condoms was found in 90% of both sexes at sexual debut. Fourteen percent of the adolescents used no contraception at all at debut in 2007, which is similar to 1986, 1993, and 2000. Eighteen percent of the pupils used no contraception at all at their last intercourse in 2007 and 2000. CONCLUSION: Knowledge about and use of condoms is substantial amongst adolescents already at sexual debut. A shift is confirmed from condoms at first coitus to more frequent use of the pill later on. A considerable number of pupils (10-20%) are neither protected against sexually transmitted infections nor pregnancy at first or later intercourse.

Gender-specific knowledge on sex.

PURPOSE: A study of what sources of knowledge on sex education, reproductive physiology and abortion was sought by adolescents at school. METHODS: A cross-sectional questionnaire study of 9th grade pupils in the municipality of Viborg, Denmark in 2007 compared with similar studies performed in 1986, 1993 and 2000. RESULTS: A total of 394 of 398 questionnaires were answered in 2007. The age of the pupils was 15.3 ± 1.5 years. In 2007, the limits for legal abortion were known by 64% of the pupils. The boys, who had had sexual debut, answered the question most correctly and the girls with no prior sexual experience the least correctly. The legal aspects of abortion in a 16-year-old girl were known by 58% of the pupils. The school was the most important source of information for the pupil without sexual debut. The adolescents who had sex indicated more use all other sources of information than those without debut. Half of the girls indicated they used magazines as a source of information, whilst only 40% of the boys mentioned pornography and magazines. The contents of girls' choice of magazines suggest that the use of written pornography as substantial source of information on sexual education. Friends/peers play a major role in sexual knowledge for both genders. CONCLUSION: In 2007, school and friends/peers still play a large role in the sexual education of the 9th grade pupils, but screen-based and magazine media whose content include substantial pornographic material share the third place.

[Long-term follow-up after endometrial ablation. A questionnaire study on bleedings, hormone treatment and surgery]. / Langtidsopfølgning efter endometrieresektion. En spørgeskemaundersøgelse om blødninger, hormonbehandling og operationer.

INTRODUCTION: Long-term follow-up 11 years after endometrial ablation. MATERIAL AND METHODS: A questionnaire on menstruation, hormone treatment, and surgery was conducted among women who had 420 endometrial ablations during the 1990-96 period; the results were analysed in conjunction with register data on cancer, surgery and obstetric history. RESULTS: A total of 82% of the questionnaires were answered. In all, 26% of the women who received hormone treatment after ablation subsequently had a hysterectomy compared with 34% of the women who received no hormone treatment after ablation (p = 0,28; chi(2)-test). Hysterectomy was associated with occurrence of meno-/metrorrhagia. However, the number of women who were hysterectomised was distributed evenly throughout the duration of hormone treatment. The time of hormone treatment according to the ablation was not associated with the distribution of meno/metrorrhagia or whether the women subsequently had a hysterectomy. We observed three women with incidental endometrial cancer at follow-up, here of one in a polyp, and the expected number was 6,8 cases. CONCLUSION: Endometrial ablation is a good treatment for menorrhagia, but in 40% of cases it is followed by further gynaecological surgery. Hormone treatment was not found to have any effect on the course of events. No additional cases of incidental cancer were noted at follow-up.

[Vaginal rupture as a late complication of hysterectomy]. / Vaginaltopruptur som senkomplikation ved hysterektomi.

We report a patient with intracoital vaginal rupture two months after a hysterectomy. The case was managed successfully by simple suturing of the vaginal vault.

[Knowledge of contraception, pregnancy, and sexuality in ninth grade pupils in the municipality of Viborg during a 21-year-period]. / Viden om praevention, graviditet og seksualitet gennem 21 år hos 9. klasser i Viborg.

INTRODUCTION: A study of the sources of and the changes in the knowledge about contraception, pregnancy, and sexuality during a 21-year-period. MATERIAL AND METHODS: A questionnaire was handed out on the same day in all ninth grade classes in the Municipality of Viborg without prior notice to teachers or pupils. The results were compared with similar studies performed in 1986, 1993, and 2000. RESULTS: In all 394 of 398 questionnaires were answered. The answers revealed that forty-three percent knew at which time in the cycle pregnancy can occur; boys with sexual debut scored lowest. The time limits for legal abortion were known by 64%, the girls had a higher level of knowledge on this item than the boys. The abortion limits for 16-year-old girls were known by 58%, but here the boys, who had made sexual debut, scored highest and the girls with no prior sexual experience scored lowest. The sources of knowledge changed over the years; screen-based media (TV, internet) now cover more than 30% of both gender's sources, and magazines/pornography comprise more than 50% of girls' and 30% of boys' sources of knowledge. The school's and friends' share in sexual education remained constant, while books and parents as knowledge sources show a downward trend. CONCLUSION: School and friends still play a substantial role in the sexual education of ninth grade pupils, but screen-based media and magazines are now the third-most important source of information and their importance have increased considerably over the past seven years. Knowledge of time limits for abortion, early pregnancy signs and cycle has not changed except for slight gender differences.

[Sexual activity and use of contraception in ninth grade pupils during the last 21 years]. / Seksuel aktivitet og praeventionsvaner hos unge gennem 21 år.

INTRODUCTION: The study surveys sexual activity, use of contraception at sexual debut and changes in sexual habits during a 21-year period. MATERIAL AND METHODS: A questionnaire was handed out on the same day in all ninth grade classes in the Municipality of Viborg. Neither teachers nor pupils were given prior notice. The results were compared with similar studies performed in 1986, 1993 and 2000. RESULTS: A total of 394 of 398 questionnaires were answered and returned. In both genders, 40% had had debuted sexually. The frequency among the boys had increased in comparison with the previous 21 years. The amount of sexual debuts before the legal age of consent at 15 years was 18%, which is similar to previous years. In both genders an increased proportion had experienced coitus within the last week. Condoms were used by 76% and the pill by 15% at sexual debut. Subsequently, 27% shifted from condom use to pill use alone or in combination with a condom at the latest coitus; thus, 34% used the pill at their latest coitus. Practical experience with condoms was found in 90% of both genders among those who had debuted sexually, while 56% of the boys and 68% of the girls indicated that they had experience with the pill. CONCLUSION: Knowledge of and use of condoms are widespread among adolescents already at sexual debut. A shift from the use of condoms to more frequent use of the pill occurs from debut to later coitus. A considerable amount of adolescents (10-20%) still do not protect themselves against sexually transmitted diseases and pregnancies at debut or later coitus.

[Sex education and knowledge of venerial disease among public school 9th graders]. / Seksualundervisning og viden om kønssygdomme hos 9. klasses elever.

INTRODUCTION: A study on knowledge of venereal diseases, opinions on sexual matters, and satisfaction with sex education at school. MATERIAL AND METHODS: A questionnaire was handed out on the same day in all ninth grade classes in the municipality of Viborg without prior notification of teachers and pupils. RESULTS: A total of 394 of 398 questionnaires were answered and returned. Only 36% were fully satisfied with the sex education imparted at school, while 70% of the teenagers were satisfied with the quantity. Satisfaction was similar between genders, but more marked among those without sexual debut as 66% were satisfied, while just 47% of those with sexual debut thought sex education was satisfactory (p < 0.006). Knowledge of venereal disease like hiv/aids, chlamydia and herpes simplex was high (> 80% of pupils). A total of 58% of boys and 76% of girls identified chlamydia as the most common venereal disease (p < 0.0001, girls vs. boys), while 26% of the boys and 27% of the girls answered AIDS/HIV (p < 0.75). Finally, 13% of boys and 6% of girls wrote "don't know" or did not answer the question. Having had sexual debut increased knowledge of chlamydia's status as the most common venereal disease to 85% among girls (p < 0.03). Knowledge of the symptoms and risks of chlamydia is rather limited. The girls were more aware of the fact that it may cause sterility (p < 0.001, girls vs. boys) and that it occurs symptomless (p< 0.02). The respondents' guess as to how many of the girls and boys had experienced sexual debut was not associated with gender but with own sexual debut. Those with no sexual debut guessed better than the pupils with sexual debut, as 77% of boys and 81% of girls with no sexual debut guessed correctly. CONCLUSION: The sex education curriculum should be differentiated with regard to sexual debut or not in order to increase satisfaction with teaching and increase the school's contribution to improve sexual knowledge and behaviour.

Surgery and cancer after endometrial resection. Long-term follow-up on menstrual bleeding and hormone treatment by questionnaire and registry.

PURPOSE: Long-term follow-up 11 years after endometrial ablation. METHODS: A questionnaire on menstruation, hormone treatment, and operations on women, which had 421 endometrial ablations during 1990-1996, was added to registered data on cancer, operational and obstetrical history. RESULTS: Eighty-two percent of the questionnaires were returned and answered. Of those women on hormone treatment after ablation 26% had a hysterectomy later on compared to 34% of women with no hormone treatment after ablation (P = 0.28; chi (2) test). Hysterectomy was directly proportional to the amount of meno/metrorrhagia; however, the number of women with a hysterectomy was evenly distributed in relation to the duration of hormone treatment. The time of hormone treatment in relation to the ablation was not associated with the distribution of meno/metrorrhagia or whether the women had a hysterectomy later on. We observed three women with incidental endometrial cancer at follow-up and the expected numbers were 6.8 cases. CONCLUSION: Endometrial ablation is an effective form of treatment for menorrhagia with no increase in the incidence of endometrial cancer. Hormonal treatment does not seem to have any influence on the course of events.

Adaptation to climate change in developing countries.

Adaptation to climate change is given increasing international attention as the confidence in climate change projections is getting higher. Developing countries have specific needs for adaptation due to high vulnerabilities, and they will in this way carry a great part of the global costs of climate change although the rising atmospheric greenhouse gas concentrations are mainly the responsibility of industrialized countries. This article provides a status of climate change adaptation in developing countries. An overview of observed and projected climate change is given, and recent literature on impacts, vulnerability, and adaptation are reviewed, including the emerging focus on mainstreaming of climate change and adaptation in development plans and programs. The article also serves as an introduction to the seven research articles of this special issue on climate change adaptation in developing countries. It is concluded that although many useful steps have been taken in the direction of ensuring adequate adaptation in developing countries, much work still remains to fully understand the drivers of past adaptation efforts, the need for future adaptation, and how to mainstream climate into general development policies.

[Analysis of need for sick leave after hysterectomy]. / Vurdering af rekreationsbehovet efter hysterektomi.

INTRODUCTION: The recommended sick leave after hysterectomy varies among operating wards and depends on many non-medical issues. The recommendation is rarely validated scientifically and is often without any connection to the women's actual handling of the leave if this is not recorded as part of a project. We analysed the postoperative period for a group of hysterectomised women who kept a diary over eight weeks. MATERIALS AND METHODS: Between July 2005 and June 2006 all hysterectomised women entered the diary project if they fulfilled the following criteria: the operation was indicated by meno-metrorrhagia, dysplasia, pressure symptoms or pain, she was under 60, she was Danish-speaking and in full-time work which was to be recommenced after operation. Women were excluded if they were operated for descended uterus, if a major re-operation was performed or, unexpectedly, endometriosis or malignancy was found. Our ward's recommendation on sick leave was four weeks for vaginal hysterectomy and six weeks for abdominal hysterectomy, but with emphasis on the necessary individualization of sick leave. Once a week, the women answered eight questions on their well-being and activities in the diary and returned the diary. RESULTS: In total, 71 women entered the study, 27 with vaginal hysterectomy and 44 with abdominal hysterectomy. After one week, none of the women suffered from nausea or discomfort, while 20% were still complaining of pain. Less than half of the women had commenced work one week after the recommended sick leave. At that time, two thirds had recommenced their former leisure activities but less than half of the women's sex lives were as before the operation. CONCLUSION: The majority of women extend their sick leave beyond the recommended period on their own initiative, despite the ward's long recommended period of sick leave. It is questionable whether the actual period of sick leave can be cut by shortening the recommended sick leave.