[music] narrator: coming up on "21st century," saving teens from pregnancy in the dominican republic. in brazil, descendants of slaves face a struggle for land. and from the united kingdom, a young woman takes on climate change. girls becoming mothers when they're still children themselves. [speaking spanish]

narrator: wrecking young lives. [speaking spanish] narrator: from the dominican republic, where nearly a quarter of all pregnancies are to teenagers, a campaign to change girls' futures. [music]

[speaking spanish]

[speaking spanish]

[speaking spanish]

[music] narrator: in brazil, a centuries-old legacy, communities created by slaves. [speaking spanish] narrator: but now that legacy is being challenged. descendants of slaves face a fight to keep hold

of their land. [speaking spanish] narrator: a way of life in jeopardy. [music] narrator: professor helio santos is president of the foundation for racial equality, a non-governmental organization in brazil.

narrator: african slavery was big business in brazil. treated more as commodities than human beings, black slaves became a major part of international trade during colonialism and boosted the country's economy. narrator: salvador de bahia, brazil's first capital city, was one of the major slave markets during the colonial era. its dark history has repercussions today. [speaking spanish] narrator: richard torciano is a director at incra, brazil's national institute for colonization and agrarian

reform. narrator: quilombolas were runaway slaves who escaped from plantations and established their own settlements on small areas of agricultural land. these settlements are known as quilombos, and many exist to this day.

narrator: 34-year-old sandra desantos is a quilombola and community leader. the quilombo where she's always lived is called danda. her grandfather created it. but today, sandra is involved in a bitter fight to preserve her family's way of life. narrator: the woman told sandra

that she was the granddaughter of the landowner. this kind of dispute has become more common in recent years as farmers have come forward to claim legal ownership of potentially profitable land. over the past century, farming families occupied lands in rural areas but often neglected them until real estate values started to surge. in some cases it's emerged that ownership documents have been forged. narrator: sandra feared that tractors would come and destroy their crops, so she brought together members of her community, and they appointed her to settle the dispute.

narrator: sandra turned to richard torciano at incra to find out more about a new clause that she stumbled upon while researching land laws--something that could save the quilombo. narrator: but the new law passed under brazil's 1988 constitution was not acted on for years. then, in 2009, former president lula da silva took a bold step

that favored the quilombolas such as sandra and her community. narrator: this meant that the quilombolas were granted legal ownership of these territories. a further symbolic recognition of the contribution of slaves to brazil's history has come from the united nations, which declared an international decade for people of african descent in january 2015. the theme of the decade is "recognition, justice, and development."

narrator: professor santos knows that even though slavery has ended, the struggle of the descendants of slaves continues. but sandra is determined and confident that her community will stay. [all singing]

narrator: coming up on "21st century," in their own words. [music] [indistinct chatter] narrator: climate change, pollution, and melting glaciers. what can one individual do? filmmaker abbie barnes' story with her own images, in her own words. [music] abbie: my name is abbie, i'm 18 years old, and i live in the southwest of england. i've always had a very deep connection with the natural world around me and very much been aware of my position within

it. it wasn't until i was about 13, though, that i began to be made aware of all of the different issues--environmental issues--that are going on around the world. and it made me feel very angry. i could not comprehend why anybody would want to destroy what in my eyes was a priceless beauty for the sake of business. and i felt i had to speak up about it, and i started to do that through the use of film. there are two main projects i'm particularly proud of. the first is my short film about marine debris called "save our oceans." i produced this when i was 15, 16. i'm talking about plastic. all: save our oceans! abbie: i arranged a beach cleanup. i sought to involve my local community. i got news of the issue out onto my local radio stations, into my local newspapers. and i really just tried to get as many people involved and aware of the issue as possible. so the second project i'm most proud of is my climb up mount kilimanjaro in

july 2014. and we were making a film about global climate change and the effect of global climate change on the mountain and the people around it. global climate change is what it says it is. it's global. it's worldwide atmospheric alteration. and every single person is playing their part no matter how insignificant it is. in the last 20 years, 70% of mount kilimanjaro's glaciers have disappeared, gone completely. after gaining a greater understanding of the issue, i really feel that it is big, but it is controllable if we all make small changes to our everyday lifestyle. if you choose to leave the tap on whilst doing your teeth, you could indirectly be affecting somebody on the other side of the planet. how? well, our earth is immensely interconnected, more so than i think we could ever begin to comprehend. and if we mess with those systems, which we are, there are going to be negative consequences. but

the thing that really motivates me most, that really drives me on, is when i receive feedback. when people come to me personally, and they're completely hooked on that subject, and they want to do everything they can to help, and that really drives me forward because i feel that modern day society has kind of a complacency, an assumption that we can continue the way we're going forever. but we are not living a sustainable way of life, and that is just not possible. [music] time is kind of running out. heh.

i feel that the greatest threat we face as a species is ourselves if we continue to ignore the things that we cannot see--global climate change, plastics in the ocean. we need to act now in order to ensure that the future generations, and that my generation, can continue to access this beautiful natural wonder around us. it's our life system. it's our life support. and without it, we just cannot exist. you can be taking action against all of these issues on our earth, and you are responsible, i am responsible, we are all responsible. yes! awúwóóóóó8úxúóóóañógñtñxñú

jacques: everyone wants to be thin. it means beauty, success, desirability, and yet 60% of us are overweight. in the middle of an obesity crisis the multi-billion pound weight loss business is bigger than ever. i'm jacques peretti, and in this series i'm going to investigate the men who've made their fortunes by selling us the dream of being thin through diets