Why do humans remove woodland

That disruption leads to more extreme temperature swings that can be harmful to plants and animals. Yet the effects of deforestation reach much farther. The South American rainforest, for example, influences regional and perhaps even global water cycles, and it's key to the water supply in Brazilian cities and neighboring countries.

The Amazon actually helps furnish water to some of the soy farmers and beef ranchers who are clearing the forest. In terms of climate change, cutting trees both adds carbon dioxide to the air and removes the ability to absorb existing carbon dioxide. If tropical deforestation were a country, according to the World Resources Institute , it would rank third in carbon dioxide-equivalent emissions, behind China and the U. The numbers are grim, but many conservationists see reasons for hope.

A movement is under way to preserve existing forest ecosystems and restore lost tree cover. Organizations and activists are working to fight illegal mining and logging—National Geographic Explorer Topher White, for example, has come up with a way to use recycled cell phones to monitor for chainsaws. In Tanzania, the residents of Kokota have planted more than 2 million trees on their small island over a decade, aiming to repair previous damage.

And in Brazil, conservationists are rallying in the face of ominous signals that the government may roll back forest protections. For consumers, it makes sense to examine the products and meats you buy, looking for sustainably produced sources when you can. Nonprofit groups such as the Forest Stewardship Council and the Rainforest Alliance certify products they consider sustainable, while the World Wildlife Fund has a palm oil scorecard for consumer brands.

All rights reserved. Climate Deforestation Forests cover about 30 percent of the planet's land mass, but humans are cutting them down, clearing these essential habitats on a massive scale. What is deforestation? Find out the causes, effects, and solutions. Most woodland in the UK is composed of blocks of similar age trees. As these trees grow they tend to reduce the light reaching the forest floor this is particularly true if the woodland has been planted close together as a timber crop. Reducing the light at ground level will reduce the number of different species able to survive in the woodland, which will have the effect of reducing the habitat diversity.

In a natural woodland this situation would hardly ever arise because of the uneven age structure of the woodland, and if it did, it would only be as one of a large number of different habitats in an area supporting a healthy ecosystem. The nature of UK woodlands means that to retain the broad variety of habitats needed for our native wildlife, we often need to manage our woodlands to mimic and recreate the mosaic of habitats present in natural woodlands.

UCS estimates that an area the size of Switzerland 14, square miles, or 38, square km is lost to deforestation every year. Natural fires in tropical forests tend to be rare but intense. Human-lit fires are commonly used to clear land for agricultural use. First, valuable timber is harvested, then the remaining vegetation is burned to make way for crops like soy or cattle grazing. In , the number of human-lit fires in Brazil skyrocketed. Many forests are cleared to make way for palm oil plantations.

Palm oil is the most commonly produced vegetable oil and is found in half of all supermarket products. It's cheap, versatile and can be added to both food and personal products like lipsticks and shampoo.

Its popularity has spurred people to clear tropical forests to grow more palm trees. Growing the trees that produce the oil requires the leveling of native forest and the destruction of local peatlands — which doubles the harmful effect on the ecosystem.

Forests can be found from the tropics to high-latitude areas. Forests provide more than a home for a diverse collection of living things; they are also an important resource for many around the world.

In countries like Uganda, people rely on trees for firewood, timber and charcoal. Monospecific stands of Colophospermum mopane dominate the region, along with occasionally co-occurring species such as Combretum apiculatum , C.

The 45 sites 1 km 2 grid; top right contained circular sampling plots m apart. Point counts for birds were undertaken in the centre of plots bottom right. Within each plot, four 1 m 2 quadrats divided into 16 blocks bottom right were used for ground vegetation surveys. The inset shows regional context—mopane woodlands light grey in Zambia black and southern Africa.

At the beginning of the dry season May—July we measured woodland vegetation structure and disturbance in plots clustered within 45 sites grids of 1 km 2. At the centre of plots from 30 sites, we collected bird diversity data using point-counts.

Each site except one for the woodland structure, where we could measure only 2 plots contained 4 circular plots m apart. To estimate ground vegetation cover hereafter ground cover , we used four smaller quadrats of 1 m 2 placed within the circular plot, one in each cardinal direction, and at 10 m from the centre.

Each ground cover quadrat was subdivided into 4 blocks such that in each circular plot, the quadrats together constituted a total of 16 blocks. The number of blocks occupied by ground vegetation was used as an index of ground cover. For unidentified trees, photographs and sample specimens were collected for identifications with help of botanists in Lusaka and online floras Bingham et al. Ground cover C , the proportion of the total number of blocks covered by ground vegetation.

Bird data were collected at the centre of each circular plot between 6 and 9 am by the point-sampling presence-absence survey method Gregory et al. For each recorded species, we collected trait information from Elton Traits 1.

The trait values were the relative percentages of 10 diet and seven foraging strata categories, activity time categorical, 1 or 0 and body mass g —table of traits provided in supplementary information SI; Table S1. For four unidentified species, mean values were used the analysis was also conducted after removing the unidentified species; this did not make any significant difference, so only results using the mean values are presented.

For functional diversity, we first made a Bray—Curtis pairwise functional distance matrix of species. We counted the number of stems impacted by elephants, evidenced by knocked down, pollarded, broken, or bark-stripped stems, and affected by humans, evidenced by cut stems.

We also derived mean pairwise geographical distance g between plots to account for spatial autocorrelation. The human population density of the study region has doubled since the s Ohadike and Tesfaghiorghis ; Hoare and Toit whilst the population of elephants has reduced fold Kampamba et al.

As human population increased, elephant densities reduced and their distribution became restricted to the few protected areas Boer et al. In this study, therefore, the elephant-dominated areas—mainly national parks, represent the early stage in this transition to human domination, whilst non-protected areas near towns represent the final stage of transition.

To examine the effects of disturbance on woodland structure and bird diversity, we constructed mixed models. We used each of the woodland structure Eq. To explain the community-level patterns of bird diversity better, we also investigated the effects of disturbance on species presence Eq. For all woodland structure and bird diversity variables except species richness , we fitted a linear mixed model with normal distribution. We assessed the habitat and diversity variables for normality, and subsequently log 10 - hereafter log transformed the non-normal variables, N, N s , B , and D.

For bird species richness and incidence, we fitted Poisson and Bernoulli random-effect models, respectively. The first 25, iterations were discarded as burn-into remove transient states and attain equilibrium distribution. From the remaining 50, total iterations, we selected samples after every 50 iterations thinning , thus yielding samples from all three chains for posterior inference.

Analyses were conducted using R statistical software version 3. We used the vegan package Oksanen et al. For FD we used the codes by Swenson Figures were drawn using ggplot2 Wickham We recorded a total of tree stems belonging to 75 species with mean DBH of The stem-size distribution in this study followed the typical reverse-j shaped, characterized by the dominance of stems in smaller size classes followed by decreasing number of stems of larger size classes. Stem-size distribution differed between human- and elephant-dominated areas.

In comparison to the low disturbance plots, the human-dominated plots contained fewer number of large-size stems Fig. Stem size distributions under different disturbance regimes. As expected, both I Human and I Ele were negatively associated with stem density, but they affected woody biomass, mean DBH, and small-stem density differently Fig. The small-stem density significantly increased with I Human Ground cover increased with mean geographic distance between plots and did not show any significant relationship with I Human or I Ele.

The effect of disturbance regime on woodland structure in 20 m radius plots. Colours indicate type of the impact—elephant blue and human orange. Both human and elephant disturbance were associated with reducing stem density but had dissimilar effects on other attributes of the woodland structure. Examples of mopane woodland under different disturbance regimes. The mopane woodlands with relatively low disturbance a have relatively high stem density and a mixture of stems of different size classes.

In the more human-affected woodlands b , large trees are selectively harvested, leading to reduced density, loss of woody biomass, and an increase in small-stem density. Elephant-dominated woodlands c contain smaller stems which are frequently browsed by elephants, and occasional stems of larger size classes which have escaped elephant impact.

These large stems maintain the plot-level woody biomass. I Human and I Ele were both associated with declining bird species richness but affected the other bird diversity variables differently Fig.

The effect of disturbance agent on species and functional bird diversity. Both human red line and elephant blue disturbances were associated reductions in species richness, but only human disturbances were associated with significant declines in functional bird diversity. The species negatively affected by I Ele were primarily insectivorous habitat generalists Terpsiphone viridis and Tchagra australis , non-mopane species Prionops retzii, Merops pusillus and species associated with regrowing woodlands Camaroptera brachyura and Prinia subflava.

Those that increased with I Ele were mainly woodland-preferring seed eaters and ground foragers mopane specialists Agapornis lilianae and Emberiza flaviventris , woodland-specific insectivores Lamprotornis mevesii and Nectarinia amethystina , and plant-eating habitat generalists Estrilda astrild. In contrast, the I Human positively affected bird species were the insectivorous habitat generalists Cisticola fulvicapilla, Uraeginthus angolensis, Salpornis spilonotus, and Lanius collaris and farmland-grassland preferring seed eaters Euplectes orix and Quelea quelea.

The negatively affected species in response to I Human mainly contained a large pool of woodland-specific birds—fruit, nectar and other plant-part eaters Estrilda astrild, Anthreptes collaris, Lybius torquatus, Nectarinia senegalensis, Serinus mozambicus, Trachyphonus vaillantii, Urocolius indicus , ground foragers Bucorvus cafer, Francolinus adspersus, and Francolinus coqui and insectivores mopane specialists Parus niger and Thripias namaquus; Batis molitor, Chrysococcyx klaas, Clamator levaillantii, Dendropicos fuscescens, and Eurystomus glaucurus.

Thus, I Ele was primarily associated with declines in non-woodland birds, whereas I Human was associated with reductions in woodland-specific birds Fig. The effect of human and elephant disturbance on species presence. For both disturbance there are more losses than gains in species incidence probability.

Inclusion of environment variables did not make any difference to our results; in other words, environmental variables are not contributing to the differences we detected.