Gabon’s large trees store huge amounts of carbon. What must be done to protect them



Ivanov Gleb/Shutterstock

John Poulsen, Duke University

Large trees are the living, breathing giants that tower over tropical forests, providing habitat and food for countless animals, insects and other plants. Could these giants also be the key to slowing climate change?

The Earth’s climate is changing rapidly due to the buildup of greenhouse gases, like carbon dioxide, in the atmosphere as a result of human activities. Trees absorb carbon from the air and store it in their trunks, branches, and roots. In general, the larger the tree, the more carbon it stores.

Globally, tropical forests remove a staggering 15% of carbon dioxide emissions that humans produce. Africa’s tropical forests – the second largest block of rainforest in the world – have a large role to play in slowing climate change.

But large trees are in trouble everywhere. I carried out research to examine the distribution, drivers and threats to large trees in Gabon. Gabon has 87% forest cover and is the second most forested country in the world.

By carrying out this project, I was able to identify areas with a wealth of large trees (and therefore key carbon stores and sinks), what needed to be done to better protect them and eventually recommend those areas as a priority for conservation.

National inventory

In 2012, the government of Gabon began a national inventory of its forests to measure the amount of carbon stored in its trees – one of the first nationwide efforts in the tropics.

An inventory of this scale isn’t easy, especially in a heavily forested country. Technicians from Gabon’s National Parks Agency travelled to every corner of the country, sometimes hiking more than two days crossing swamps and traversing rivers, to measure the diameter and height of trees in plots a bit larger in size than a soccer field.

Using Gabon’s new inventory of 104 plots, we calculated the amount of carbon in 67,466 trees, representing at least 578 different species. We did this by applying equations to the tree measurements.

The results indicated that the density of carbon stored in Gabon’s trees is among the highest in the world. On average, Gabon’s old growth forests harbour more carbon per area than old growth forests in Amazonia and Asia.

Most of this carbon is stored in the largest trees – those with diameters bigger than 70cm at 1.3 meters from the ground. Just the largest 5% of trees stored 50% of the forest carbon. In other words, 3,373 trees out of the 67,466 measured trees contained half of the carbon.

Drivers of forest carbon stocks

Next, we examined the drivers of carbon stocks. What determines whether an area of forest holds many large trees and lots of carbon? Do environmental conditions or human activities have the largest impact on forest carbon stocks?

Environmental factors – such as soil fertility and depth, temperature, precipitation, slope and elevation – often influence the amount of carbon in a forest. During photosynthesis, trees harness energy from the sun to convert water, carbon dioxide, and minerals into carbohydrates for growth. Therefore, forests with low levels of soil minerals or that receive little rainfall should store less carbon than areas with abundant minerals and water.

Human activities – like agriculture and logging – also influence carbon stocks. Cutting down trees for timber, to clear land for farming, or for construction reduces the amount of carbon stored in forests.

We examined the amount of carbon in each tree plot in relation to the environmental factors and human activities associated with the plot. Surprisingly, we found that human activities, not environmental factors, overwhelmingly affect carbon stocks.

The impact of human activities on forest carbon was largely unexpected because of Gabon’s high forest cover (the second highest of any country) and low population density (9 people per square kilometer), 87% of which is located in urban areas. If human impacts are this strong in Gabon, what must their effects be in other tropical nations?

Although we don’t know for sure, we believe past and present swidden (slash-and-burn) agriculture is the principle cause for low carbon stocks in some areas. Forests close to villages had lower levels of carbon, probably because forest clearing for farming converts old growth forest to secondary forest.

Interestingly, forests in logging concessions held similar amounts of carbon as old growth forests. It is too early to conclude that timber harvest doesn’t reduce carbon levels by cutting large trees, but this finding gives hope that logging concessions can be managed sustainably to conserve carbon stocks.

Importantly, forests in national parks stored roughly 25% more carbon than forests outside of parks. Thus, protecting mostly undisturbed forests can effectively conserve carbon and biodiversity.

Saving Gabon’s giants

The critical role of humans in diminishing carbon stocks is both a blessing and a curse. One one hand, the future of forests are in our hands, giving us the power to choose our fate. On the other hand, we cannot ignore the responsibility to act collectively to secure these resources while considering the interests of the countries that host them.

Gabon is taking laudable actions to conserve its forests, including a protected area network of 13 parks. In addition, Gabon is reforming its logging sector and developing a nationwide land use plan. These actions are a great start, yet continued action is necessary to curb the effects of swidden agriculture and ensure that growing industrial agriculture does not reverse Gabon’s achievements.

Intact forests can pay returns. Norway recently committed to paying Gabon $150 million for stewardship of its forests. Conservation of forests requires sacrifice by the Gabonese people. Yet, this payment demonstrates that Gabon’s large trees are a national asset that can contribute to its development as well as an international resource requiring collective action to conserve.The Conversation

John Poulsen, Associate Professor of Tropical Ecology, Duke University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Yes, SA’s battery is a massive battery, but it can do much more besides


Dylan McConnell, University of Melbourne

Last Friday, the “world’s largest” lithium-ion battery was officially opened in South Australia. Tesla’s much anticipated “mega-battery” made the “100 days or it’s free” deadline, after a week of testing and commissioning.

Unsurprisingly, the project has attracted a lot of attention, both in Australia and abroad. This is largely courtesy of the high profile Tesla chief executive Elon Musk, not to mention the series of Twitter exchanges that sparked off the project in the first place.

Many are now watching on in anticipation to see what impact the battery has on the SA electricity market, and whether it could be a game-changer nationally.

The Hornsdale Power Reserve

The “mega battery” complex is officially called the Hornsdale Power Reserve. It sits alongside the Hornsdale Wind Farm and has been constructed in partnership with the SA government and Neoen, the French renewable energy company that owns the wind farm.

The battery has a total generation capacity of 100 megawatts, and 129 megawatt-hours of energy storage. This has been decribed as “capable of powering 50,000 homes”, providing 1 hour and 18 minutes of storage or, more controversially, 2.5 minutes of storage.

At first blush, some of these numbers might sound reasonable. But they don’t actually reflect a major role the battery will play, nor the physical capability of the battery itself.

What can the battery do?

The battery complex can be thought of as two systems. First there is a component with 70MW of output capacity that has been contracted to the SA government. This is reported to provide grid stability and system security, and designed only to have about 10 minutes of storage.

The second part could be thought of as having 30MW of output capacity, but 3-4 hours of storage. Even though this component has a smaller capacity (MW), it has much more storage (MWh) and can provide energy for much longer. This component will participate in the competitive part of the market, and should firm up the wind power produced by the wind farm.


Read more: Australia’s electricity market is not agile and innovative enough to keep up


In addition, the incredible flexibility of the battery means that it is well suited to participate in the Frequency Control Ancillary Service market. More on that below.

The figure below illustrates just how flexible the battery actually is. In the space of four seconds, the battery is capable of going from zero to 30MW (and vice versa). In fact it is likely much faster than that (at the millisecond scale), but the data available is only at 4-second resolution.

Hornsdale Power Reserve demonstrating its flexibility last week. The output increased from zero to 30MW (full output) in less than 4 seconds.
Author provided (data from AEMO)

Frequency Control and Ancillary Service Market

The Frequency Control and Ancillary Service (FCAS) market is less known and understood than the energy market. In fact it is wrong to talk of a single FCAS market – there are actually eight distinct markets.

The role of these markets is essentially twofold. First, they provide contingency reserves in case of a major disturbance, such as a large coal generation unit tripping off. The services provide a rapid response to a sudden fall (or rise) in grid frequency.

At the moment, these contingency services operate on three different timescales: 6 seconds, 60 seconds, and 5 minutes. Generators that offer these services must be able to raise (or reduce) their output to respond to an incident within these time frames.

The Hornsdale Power Reserve is more than capable of participating in these six markets (raising and lowering services for the three time intervals shown in the illustration above).

The final two markets are known as regulation services (again, as both a raise and lower). For this service, the Australian energy market operator (AEMO) issues dispatch instructions on a fine timescale (4 seconds) to “regulate” the frequency and keep supply and demand in balance.

The future: fast frequency response?

Large synchronous generators (such as coal plants) have traditionally provided frequency control, (through the FCAS markets), and another service, inertia – essentially for free. As these power plants leave the system, there maybe a need for another service to maintain power system security.

One such service is so-called “fast frequency response” (FFR). While not a a direct replacement, it can reduce the need for physical inertia. This is conceptually similar to the contingency services described above, but might occur at the timescale of tens to hundreds of milliseconds, rather than 6 seconds.


Read more: Baffled by baseload? Dumbfounded by dispatchables? Here’s a glossary of the energy debate


The Australian Energy Market Commission is currently going through the process of potentially introducing a fast frequency response market. In the meantime, obligations on transmission companies are expected to ensure a minimum amount of inertia or similar services (such as fast frequency response).

I suspect that the 70MW portion of the new Tesla battery is designed to provide exactly this fast frequency response.

Size matters but role matters more

The South Australian battery is truly a historic moment for both South Australia, and for Australia’s future energy security.

The ConversationWhile the size, of the battery might be decried as being small in the context of the National Energy Market, it is important to remember its capabilities and role. It may well be a game changer, by delivering services not previously provided by wind and solar PV.

Dylan McConnell, Researcher at the Australian German Climate and Energy College, University of Melbourne

This article was originally published on The Conversation. Read the original article.

Tundra and Climate Change


The link below is to an article that reports on concerns of carbon stored in the Tundra regions of the north once it thaws with climate change.

For more visit:
http://www.enn.com/climate/article/45987

Article: Seagrasses Store Massive Amounts of Carbon


The following link is to an article that looks at how much carbon is stored by seagrasses.

For more visit:
http://www.treehugger.com/climate-change/seagrasses-can-store-twice-carbon-forests.html