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Go to Brilliant.org/SciShow to  check out their Logic course and for 20% off an annual premium subscription. [♪ INTRO] Stem cells have an important  role throughout our bodies, replenishing other cells to  keep our tissues healthy. But, just like our bodies as a whole, stem  cells can age and lose their function.

This aging process isn’t entirely  understood, but a new study in the journal Science Advances indicates that stem  cell function has to do with their size. It turns out that, for stem cells,  the bigger they are, the harder… it is for them to do their job. This study specifically looked  at hematopoietic stem cells, the ones that produce new blood cells.

These blood stem cells are some of  the smallest cells in our bodies, but the longer they’re around, the more  they divide and replicate their DNA, and the more often that DNA incurs damage. Now, cells can repair damaged DNA to some extent. And during repair, these stem  cells continue to grow in size.

So, as they get older, they tend to get larger. And these larger, older cells tend not to  be as good at generating new blood cells. This is true in us humans, as well  as in other mammals such as mice.

Now, you might think that loss of  function has to do with their damaged DNA, but this study actually showed it  has to do with their larger size. When researchers treated blood  stem cells from mice with a drug called rapamycin, which prevents cell growth, the cells stayed small and  maintained normal functioning, even after developing and repairing DNA damage. On top of that, the researchers  bred mice with a mutation that reduced their ability to  protect against DNA damage.

Without the mutation, cells aged and  grew larger in response to damage. But with it, the cells stayed small and  kept dividing, even with the damaged DNA. Now, this may seem like a strange correlation,  but the researchers think it might have to do with the amount  of space inside the cell.

The larger the cell, the more sparsely  distributed certain proteins are, which might make it harder for  cells to function properly. But this might not just be a  fluke of a cell’s life cycle. This aging process might serve a purpose.

See, as cells accumulate genetic  damage, they run the risk of becoming cancerous, dividing  and proliferating uncontrollably. So, maybe a loss of function with age works to help keep cancerous growth in check. All in all, this is an important step in  understanding the details of cellular aging.

With more study, researchers might  be able to develop treatments to restore the function of blood stem cells. That could help lead to treatments for  people with blood-related diseases. And if the same rules about cell size  hold true for other types of stem cells, these sorts of treatments could  be even more broadly useful.

But let’s turn from revitalizing our  bodies, to revitalizing our environment. A new study in Nature Sustainability  provides an assessment of the Great Green Wall program, a major effort to restore  degraded ecosystems across Africa. The program was started in 2007 under  the leadership of the African Union, and now includes the concerted efforts  of more than 20 African countries.

And the news is promising for  the effort’s long-term success. Here’s some background: the Sahel  region is a belt that stretches across sub-Saharan Africa from the  Atlantic Ocean to the Red Sea. It’s an area that suffers from a  great deal of land degradation.

The climate crisis has hit the region  hard, and that’s led to a lot of the land becoming less suitable for  farming and productivity. This is bad for biodiversity, but also for the humans who rely on  the land for food, jobs, and stability. The Great Green Wall is a massive initiative  to create a coast-to-coast band of improved environments across the region,  aiming to restore the land by planting trees, revitalizing grasslands,  and a variety of other efforts.

Since its origins in 2007, the  program has restored landscapes across 4 million hectares, but the ultimate goal  is to cover 100 million hectares in total. This new study is an assessment of the initiative: what’s been done so far, what  obstacles need to be overcome, and what the overall benefits will be. The study is very comprehensive,  and it includes a lot of discussion about the political side of  environmental preservation.

They note, for example, how  important it is to have cooperation between multiple governments and private  landowners in order for land restoration to have lasting effects. And unfortunately, they also point  out that one of the major obstacles in the way of the project has  been conflict in the region, which can hinder access to key environments. And, of course, they discuss money.

A major project like this requires  major funding, which can be a hurdle. Fortunately, money can also be a motivator. And this assessment indicates  that if the project is done right, it won’t only be good for the  environment, but for the economy as well.

The study estimates that over several  years, every investment of of one US dollar will ultimately return, on average, a dollar and twenty cents  under their base scenario. And since they estimate a total cost  of between 20 and 70 billion dollars for the entire restoration plan, that’s  quite an economic benefit to look forward to, and hopefully a good incentive for funders. The Great Green Wall has the potential  to improve the lives of people all across the Sahel region, and to improve the resilience of nature in  the face of dangers like climate change.

And this study tells us what it will  take for it to really be a success. But it seems like the prospects are good. Of course, this is a massive effort, and it’s never simple to  solve these kinds of problems.

But we can sharpen our problem-solving  skills, with help from Brilliant. Brilliant is an online learning  platform with courses about science, engineering, computer science and math. They’ve just relaunched their Logic  course with a new coat of polish and way more interactivity than before.

It’ll show you how to make predictions  based on limited information, by logically eliminating incorrect possibilities. If you’d like to give Brilliant a try,  you can sign up at Brilliant.org/SciShow to save 20% off an annual premium subscription. Checking them out supports us too, so thank you! [♪ OUTRO]