Climate change is happening due to natural factors and human activities. It expressively alters biodiversity, agricultural production, and food security. Mainly, narrowly adapted and endemic species are under extinction. Accordingly, concerns over species extinction are warranted as it provides food for all life forms and primary health care for more than 60–80% of humans globally. Nevertheless, the impact of climate change on biodiversity and food security has been recognized, little is explored compared to the magnitude of the problem globally. Therefore, the objectives of this review are to identify, appraise, and synthesize the link between climate change, biodiversity, and food security. Data, climatic models, emission, migration, and extinction scenarios, and outputs from previous publications were used. Due to climate change, distributions of species have shifted to higher elevations at a median rate of 11.0 m and 16.9 km per decade to higher latitudes. Accordingly, extinction rates of 1103 species under migration scenarios, provide 21–23% with unlimited migration and 38–52% with no migration. When an environmental variation occurs on a timescale shorter than the life of the plant any response could be in terms of a plastic phenotype. However, phenotypic plasticity could buffer species against the long-term effects of climate change. Furthermore, climate change affects food security particularly in communities and locations that depend on rain-fed agriculture. Crops and plants have thresholds beyond which growth and yield are compromised. Accordingly, agricultural yields in Africa alone could be decline by more than 30% in 2050. Therefore, solving food shortages through bringing extra land into agriculture and exploiting new fish stocks is a costly solution, when protecting biodiversity is given priority. Therefore, mitigating food waste, compensating food-insecure people conserving biodiversity, effective use of genetic resources, and traditional ecological knowledge could decrease further biodiversity loss, and meet food security under climate change scenarios. However, achieving food security under such scenario requires strong policies, releasing high-yielding stress resistant varieties, developing climate resilient irrigation structures, and agriculture. Therefore, degraded land restoration, land use changes, use of bio-energy, sustainable forest management, and community based biodiversity conservation are recommended to mitigate climate change impacts.

Woody species are very important components of agroforestry as they play multiple roles in the system. Therefore, this study was conducted to assess woody species diversity within households' farms. Stratified random sampling was employed for the study, where households were stratified via wealth ranking. Accordingly, the farm plots of 54 households were subjected to a complete on-farm woody species inventory and identification. Consequently, the diameter at breast height (DBH) of all woody species ≥5 cm was recorded. Therefore, important value and diversity indices, density, dominance, and frequency were computed and estimated. A total of 90 woody species belonging to 80 genera and 42 families were recorded in the area. Out of the total species recorded, 2 (2.22%), 32 (35.56%), and 56 (62.22%) were endemic, exotic, and indigenous, respectively. The family Fabaceae had the highest number of woody species represented by 16. The most frequent species were Cordia africana Lam., followed by Eucalyptus camadulensis Dehnh., Persia americana Mill., Mellitia ferruginea (Hochst.) Bak., and Croton macrostachyus Del. which occurred in 87.03%, 81.48%, 81.48%, 75.92%, 72.2% of sampled farms, respectively. Besides, the top five species which had the highest important value index were Eucalyptus camaldulensis (57.38), Cordia africana (30.45), Persea americana (27.36), Mellitia ferruginea (17.28), and Croton macrostachyus (14.59). Shannon Weiner index (H') and Shannon evenness values of the study area were 2.17 and 0.80, respectively. Species richness and Shannon index values were statically significant (p < 0.05) among the three wealth categories. Besides, the Sorensen similarity index for studied villages ranged from 33.7% - to 77.5%. Generally, the current study showed that the agroforestry system plays a remarkable role in conserving woody species diversity. However, extension services on management practices for species and stands, increasing seedling accesses, and survival rates of species are very impotent to making agroforestry practices sustainable.

Background: Forests provide various ecosystem services. They are natural capitals that enhance nature to regulate itself via carbon sinks. However, anthropogenic and natural factors have altered their CO₂ sequestration and carbon storage potentials. This study is aimed for examining the effect of patch size and biomass extraction on carbon stocks in northern Ethiopia. A total of 61 sample plots measuring 20 m × 20 m size each (0.04 ha) had been systematically assigned on patches classified into three size categories. However, the numbers of plots taken per patch were different with their sizes. Moreover, stump density has been computed at each plot to estimate the difference in the level of disturbance among patches. Carbon stocks had been estimated via models previously developed. One-way ANOVA was used to examine a variation in carbon stocks and sequestration potentials. Besides, a linear regression analysis was discretely done to examine the relationship between patch sizes, disturbance level, and carbon stocks. Results: The overall aboveground biomass (ton ha⁻¹) for the studied patches was 2059.13. There was a statistically significant variation in carbon stocks (ton ha⁻¹) among patch size categories. The mean levels of disturbance ranges from 10.83% ± 1.30 to 30.8% ± 4.04. However, statistically significant difference in the level of disturbance was observed between large and small patch size categories, respectively (p < 0.05). Besides, a regression analysis confirmed a significant and negative relationship between patch size and patch disturbances (R² = 0.65, p < 0.05). However, significant positive relation between carbon stocks (ton ha⁻¹) and patch size (R² = 0.53, p < 0.05) had observed. Conclusions: In general, patch size and biomass extinction significantly influenced carbon stocks and CO₂ sequestration potentials of forests. Consequently, with the pressing need to mitigate the effects of rising atmospheric CO₂, maximizing carbon storage in the forest ecosystem is increasingly considered a viable management strategy. Therefore, disturbed land restoration, increasing forest patch size, sustainable management, and conservation of the existing remnant forest patch is needed to enhance carbon stocks and CO₂ sequestration potentials.

Environmental variables like elevation affect species composition, diversity, distribution, density, and horizontal and upward growth. Ecologists are constantly working to better understand how species diversity varies along elevational gradients, particularly in mountainous ecosystems. Therefore, the purpose of this research was to examine the species’ horizontal and vertical structural diversity along the Harego Mountain Forest’s elevational gradient. The area was categorized into lower, middle, and upper elevations. A total of 67 (20 m × 20 m) plots were created along gradients of elevation 2,079–2,516 meters above sea level (m a.s.l.). Information for floristic composition, diversity, stand structure, and environmental variables were measured and recorded for each plot over the three elevational gradients. Data on anthropogenic disturbances were visually evaluated for every plot in every gradient of elevation. For the diversity analysis, Hill’s diversity statistics were employed. To find significant variations between the three elevational gradients in terms of Hill’s diversity number, stand structure, and environmental variables, the one-way analysis of variance with SPSS version 26 at the 0.05 level of significance was carried out. The finding revealed that 50 woody plants that belonged to 35 families and 44 genera in the 67 sample plots with an elevation of 2,079 to 2,516 were identified. Shrubs were dominant in each elevational gradient. Species richness, abundance, and Hill’s diversity number were all significantly ( ) greater in the upper elevational gradient of the forest. On the other hand, all stand structures were significantly ( ) higher in the middle elevational gradient. The effect of anthropogenic disturbances and environmental variables were clearly observed in the lower and upper elevational gradients than in the middle elevation. As a result, there were fewer seedlings, saplings, trees, and shrubs in the gradients of lower and higher elevations. For the conservation of the forest, it is crucial to pay special attention to biotic elements at lower elevations and abiotic factors at higher elevations. Accordingly, involving the local community in forest management, reducing anthropogenic pressure in and around the Harego Mountain Forest through tree planting in farmlands and woodlots and implementing physical soil and water conservation structures are recommended.